An Australian photographer's portrait of a pot-bellied seahorse has been hailed "an incredible celebration of nature".

The gunman who killed the CEO of the largest US health insurer likely left New York City on a bus soon after the brazen ambush that has shaken corporate America, police officials said.

But he left something behind: a backpack that was discovered in Central Park.

Nearly four days after the shooting of UnitedHealthcare CEO Brian Thompson, police still did not know the gunman's name or whereabouts or have a motive for the killing.

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Investigators were looking at whether the shooter may have been a disgruntled employee or client of the insurer, Chief of Detectives Joseph Kenny told reporters.

The FBI announced on Friday night it was offering a $50,000 US ($78,200 AU) reward for information leading to an arrest and conviction.

Video of the gunman fleeing Wednesday's shooting showed him riding a bicycle into Central Park and later taking a taxi to a bus terminal that offers commuter service to New Jersey and Greyhound routes to Philadelphia, Boston and Washington, D.C, according to Kenny.

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Police have video of the man entering the bus station but no video of him exiting, leading them to believe he left the city, Kenny said.

Investigators on Friday found a backpack in the park that had been worn by the gunman during the shooting, police said, following a massive sweep to find it in a vast area with lakes and ponds, meadows, playgrounds and woods.

Police didn't immediately reveal what, if anything, it contained but said it would be analysed for clues.

The gunman made sure to conceal his identity with a mask during almost all of his time in the city, including during the attack and while he ate, yet left a trail of evidence in view of the nation's biggest city and its network of security cameras.

The gunman arrived in New York City on November 24 and shot Thompson 10 days later outside his company's annual investor conference at a hotel just blocks from Radio City Music Hall and Rockefeller Center.

The gunman got off a bus that originated in Atlanta and made several stops along the way, Kenny said. Police have not determined where he got on the bus.

Investigators have a list of passengers, but none of them would have had to provide an ID when they climbed aboard, Kenny said.

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Investigators believe the suspect used a fake identification card and paid cash, Kenny said, when he checked in at the hostel, which has a café along with shared and private rooms and is blocks from Columbia University.

Investigators have tested a discarded water bottle and protein bar wrapper in a hunt for his DNA. They also were trying to obtain additional information from a cellphone found along the gunman's escape route.

Photos of the suspected shooter that were taken in the lobby of a hostel on Manhattan's Upper West Side appear to from the only time he removed his mask, Kenny said.

The images, showing a man smiling in the lobby of the HI New York City hostel. They are among a collection of photos and video circulated since the shooting — including footage of the attack, as well as images of the suspected gunman at a Starbucks beforehand.

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"From every indication we have from witnesses, from the Starbucks, from the hostel, he kept his mask on at all times except for the one instance where we have him photographed with the mask off," Kenny said.

His roommates at the hostel also said he didn't speak to them. Nothing of investigative value was found in a search of the suspected shooter's hotel room.

Asked how close he felt police were to making an arrest, Kenny said, "This isn't 'Blue Bloods.' We're not going to solve this in 60 minutes. We're painstakingly going through every bit of evidence that we can come across. Eventually, when an apprehension is made, we will have to present all of these facts to a judge and jury, so we're taking our time, doing it right and making sure we're going to get justice for this victim and closure for his family."

Security video of the shooting shows the killer approaching Thompson from behind, firing several shots with a gun equipped with a silencer, barely pausing to clear a jam while the executive fell to the sidewalk.

Police were looking into the possibility that the weapon was a veterinary pistol, which is a weapon commonly used on farms and ranches if an animal has to be euthanised quietly, Kenny said — though he stressed that hadn't been confirmed.

The words "delay," "deny" and "depose" were scrawled on the ammunition, one word on each of three bullets, Kenny said. A law enforcement official previously told The Associated Press the words were "deny," "defend" and "depose." The messages mirror the phrase "delay, deny, defend," which is commonly used by lawyers and critics about insurers that delay payments, deny claims and defend their actions.

Thompson, a father of two sons who lived in a Minneapolis suburb, had been with Minnesota-based UnitedHealthcare since 2004 and served as CEO for more than three years.

The insurer's parent company, UnitedHealth Group Inc., was holding its annual meeting in New York for investors. The company abruptly ended the conference after Thompson's death.

UnitedHealth Group said it was focused on supporting Thompson's family, ensuring the safety of employees and assisting investigators. "While our hearts are broken, we have been touched by the huge outpouring," the company said.

UnitedHealthcare provides coverage for more than 49 million Americans. It manages health insurance coverage for employers and state and federally funded Medicaid programs.

In October, UnitedHealthcare was named along with Humana and CVS in a Senate report detailing how its denial rate for prior authorizations for some Medicare Advantage patients has surged in recent years.

The shooting has rocked the health insurance industry in particular, causing companies to reevaluate security plans and delete photos of executives from their websites. A different Minnesota-based health care company said on Friday it was temporarily closing its offices out of an abundance of caution, telling employees to work from home.

Iconic Parisian monument the Notre Dame Cathedral has reopened to the public for the first time since a fire gutted the Catholic church in 2019.

The bells of Notre Dame are once again ringing in the French capital following a lavish ceremony to welcome the gothic cathedral's rebirth.

The service attracted a bevy of world leaders, among them president-elect Donald Trump, US first lady Jill Biden, Ukraine's President Volodymyr Zelensky and French President Emmanuel Macron.

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Trump was greeted by a round of applause as he entered the church and was seated next to Macron and his wife Brigitte, who provided a buffer between the president-elect and the US first lady.

Macron welcomed Trump with the pair's now infamous handshake following a private meeting before the ceremony.

Tesla billionaire Elon Musk also attended the church ceremony as one of several VIP guests alongside Prince William, actress Salma Hayek and LVMH founder and chief executive Bernaud Arnault.

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The Prince of Wales and Trump met later in the evening at the UK ambassador's residence in Paris.

Trump described William as a "good man" and said he is "doing a fantastic job".

Notre Dame has officially reopened more than five years after a devastating fire destroyed its roof and famous spire in April 2019.

It took five years of frenetic construction work to recreate the soaring ceilings and stonework beloved by centuries of visitors to the church's sacred grounds.

Gone are the years of scaffolding and cranes and gaping holes the blaze tore into the 861-year-old church's interior and exterior.

Macron spoke of the heartbreaking 2019 cathedral fire and the painful impact it had across the world ahead of the reopening.

"The planet was shaken on that day," Macron said.

"The shock of the reopening will – I believe and I want to believe – be as strong as that of the fire, but it will be a shock of hope."

Australian breakdancer Rachael Gunn's legal team has shut down a Raygun-inspired musical ahead of its Sydney premiere tonight.

The show was advertised as a musical parody of Raygun's journey to the Paris Games, featuring songs like I'm Breaking Down and I Would Have Won But I Pulled a Muscle.

But in the world of Raygun, it seems there's one rule – laugh with her, not at her.

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Comedian and creator of Raygun the Musical, Steph Broadbridge, told 9News the show was an homage to the athlete.

"I think it will be good for her brand, I don't think it will be bad for her brand," Broadbridge said.

Hours before tonight's premiere, Broadbridge was forced to cancel the show after Rachael Gun's lawyers threatened to sue.

"Ah shock," Broadbridge said of her reaction to the legal intervention.

"I didn't expect to be on anyone's radar at this stage in the process of being this very small musical project."

Since going viral at the Olympics for her unique brake-dancing routine, Rachael Gunn has been on a carefully crafted PR run, jumping in front of the camera for numerous media appearances.

In a statement today, Raygun's management said they were "committed to protecting her intellectual property and ensuring that her brand remains strong and respected."

Under Australian copyright law, satire and comedy are exempt under fair dealings but that didn't stop Raygun's legal team from sending the show's venue on Sydney's Oxford Street a cease and desist notice.

"While we have immense respect for the credible work and effort that has gone into the development of the show, we must take necessary steps to safeguard Rachael's creative rights and the integrity of her work," the statement said.

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"This action is not intended to diminish the contributions of others, but rather to ensure her brand is properly represented and protected in all future endeavours."

Broadbridge announced the cancellation on social media this morning and said refunds would be issued to ticket holders.

"They were very concerned that people would think that Rachael Gunn was affiliated with the musical," she said.

"I want to assure everyone that she will not be part of the show. She's very welcome to come, I would love for her to see it."

Despite the set back, Broadbridge hasn't given up on one day performing the show – with the athlete front and centre in the audience.

"I wrote every song imagining her sitting in the front row watching it," Broadbridge said.

The comedian says the offer's still open despite the legal setback.

"Of course. I want her to come more now."

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Stolen copper wires have left hundreds of homes in Adelaide's Foothills without internet for the past 48 hours. 

The wires were stolen from multiple pits on Shepherds Hill Road which caused widescale NBN outages across Eden Hills and Bellevue Heights.

Shepherds Hill Road, Offler Avenue, Sargent Parade, St Georges Terrace, Vaucluse Crescent and Silverdale Crescent have all been impacted.

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"We woke up Friday morning and no internet. That was it," Eden Hills resident Michael White said.

"Everything is offline. Even using your iPad, every time I try to get on YouTube in the morning while you eat breakfast to just watch something – but just nothing, spinning wheels," Bellevue Heights resident Joel Lawrence said.

Another 203 homes in Craigmore were also offline this morning after yet another copper theft there.

Crews are working to repair the significant damage in Eden Hills but estimate it could take three days before customers are back online.

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Contractors from Perth have been flown in to help, with more arriving tomorrow.

"I had an email from Belong which is my service provider to say that there was an outage in the area and that crews were working to get it reinstated," White said.

"So we're just sitting here thinking when's it going to come back? When's it going to work?" Lawrence said.

NBN has apologised for the inconvenience and said it's working with police to protect its infrastructure.

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The federal government is trialling a new way for Australians to prove their identity without handing over any sensitive information.

It's a world-first plan to stop identity theft. 

"We are moving from cheques to tap and go ID," Government Services Minister Bill Shorten said.

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A Brisbane medical centre is the first to use the digital ID technology dubbed the 'Trust Exchange' which will put documents and paperwork in the past.

Instead of government-issued identification including Medicare, concession and veterans cards, Australians can scan their myGov wallet and confirm their identity without creating a copy.

"It is the future," trial participant Veronica Scipioni said.

Services Australia chief customer officer Jonathon Thorpe agreed.

"This really puts people in control of what's being shared and how it's being shared and making sure that's safe and secure," he said.

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The focus is now on medical service providers but the government hopes banks, real estate agents and hotels will sign up for the voluntary program.

It comes as data breaches reached its highest level in three and a half years.

There have been 527 breaches in Australia this year, with one of those affecting more than 10 million people.

Almost 70 per cent of those were committed by criminals with malicious intent. 

"Identity fraud is a massive, multi-billion dollar issue," Shorten said.

"If someone gets their hands on your identity, it can be life-changing – and not in a good way."

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A young family has described the terrifying moment armed intruders confronted them in their Melbourne home and threatened to kill them.

Chetan Patel and his pregnant wife Rohini were in their bedroom in Truganina with their five-year-old daughter sleeping next to them when two allegedly armed men appeared at their door.

"They had a big knife and another person has (an) axe and knife and they try to threaten us by swinging the weapon," Chetan told 9News.

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"We were really, really scared. How come this has happened? How come he entered in our home? You know, you can't imagine," Rohini said.

The Patel's said the pair had allegedly jumped the fence and entered the home through the garage door before making their way upstairs.

"He's like 'Give us the car keys otherwise we're gonna kill you all. I'm gonna kill your daughter'," Chetan said.

The alleged thieves then took off in the couple's new car.

The Patel family are now living in fear over what they experienced.

The five-minute encounter left their young daughter terrified. She doesn't want to go anywhere by herself, even within her own home.

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"That's gonna live with us for our entire lifetime. The psychological or the mental stress that we have gone through from that incident," Chetan said.

"Apart from the car, what they have stolen is they've stolen our mental peace."

Police managed to track down the car just five kilometres away on Leakes Road in Tarneit.

Two men from Geelong, aged 19 and 26, were arrested. 

"Luckily, they were not minor, not under 18. If they were under 18, they can easily get relieved," Rohini said.

The pair were charged and appeared in Melbourne Magistrates Court this afternoon, where they were remanded in custody.

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OT confirm two teens missing from bootcamp found. Police found armed youths in stolen car.

A former client allegedly targeted a law firm on the New South Wales Central Coast with homemade explosives, leaving staff traumatised.

Gary Steven Middleton, 66, was arrested and charged yesterday for allegedly setting fire to two offices in Gosford using LPG cylinders on Thursday.

Several gas cylinders had been allegedly set alight inside Conditsis and Associates, causing doors to blast off their hinges and thick smoke and flames to engulf the building.

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It left the 20 staff inside at the time scrambling for safety.

Police alleged Middleton set off the homemade explosives inside the law firm, which had previously represented him, after they cut ties with him as a client.

Conditsis and Associates said staff had been left traumatised.

"The incident was traumatic for all our staff and we are so grateful that no one was seriously physically injured or worse – it was a miracle," Conditsis and Associates' director Manny Conditsis said in a statement.

The Legal Aid office on Donnison Street was also allegedly set alight just before 2.30pm on Thursday.

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Gosford Courthouse and Director of Public Prosecutions offices were temporarily closed as a precaution until police tracked down Middleton to his Wallarah home and charged him.

Middleton had been on strict bail since April and is facing a raft of serious charges.

He was due to be sentenced yesterday, a day after the alleged arson attack, for those charges.

Now, Middleton is facing two counts of destroying or damaging property with intent to endanger life, which carries a maximum penalty of 25 years imprisonment.

The 66-year-old did not apply for bail when he faced Parramatta Local Court today.

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The numbers are in for tonight’s $17 million Lotto Powerball draw.