New York police have posted a photo on social media of a person of interest as the hunt continues for a gunman in a gas mask and a construction vest who set off a smoke canister on a rush-hour subway train in Brooklyn and shot at least 10 people.
A credit card the shooter is believed to have dropped at the scene was used to rent a U-Haul van police have linked to the shooting.
Police posted a photo of Frank James, 62, who they named a person of interest.
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The van was rented on Monday from a U-Haul store in Philadelphia, according to company records obtained by CNN.
The rental agreement obtained by CNN shows the U-Haul reservation was made Wednesday, and was scheduled to be picked up Monday at 2.01pm local time.
The van was supposed to be rented for two days, according to the reservation.
The NYPD's bomb squad is responding to the Brooklyn scene where the U-Haul truck was found, a law enforcement source told CNN.
U-Haul said it is working with authorities.
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Chief of Detectives James Essig said investigators weren't sure whether Mr James had any link to the subway attack.
Authorities were looking at his apparent social media posts, some of which led officials to tighten New York Mayor Eric Adams' security detail.
Police Commissioner Keechant Sewell called the posts "concerning."
Rambling, profanity-filled YouTube videos apparently posted by Mr James, who is Black, are replete with Black nationalist rhetoric, violent language and bigoted comments, some of them directed at other Black people.
One, posted April 11, rails against crime against Black people and says drastic action is needed to change things.
Another, from March 20, says the nation was "born in violence, it's kept alive by violence or the threat thereof and it's going to die a violent death."
A February 20 video says the mayor and governor's plan to improve safety in New York City's subway system "is doomed for failure" and refers to himself as a "victim" of the mayor's mental health program.
A January 25 video — called "Dear Mr Mayor" — is somewhat critical of Mr Adams' plan to end gun violence.
New York City agencies are offering a joint US$50,000 ($66,972) reward for any information leading to the arrest of the suspect involved in the shooting, according to a statement from the Metropolitan Transportation Authority.
Scene of horror
A scene of horror unfolded as frightened commuters ran from the train as others limped out of it.
At least one rider collapsed on the platform.
"My subway door opened into calamity. It was smoke and blood and people screaming," eyewitness Sam Carcamo told radio station 1010 WINS.
Smoke poured out of the train car as the door opened, he added.
Five people were in critical condition but expected to survive.
At least 29 in all were treated at hospitals for gunshot wounds, smoke inhalation and other conditions.
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The gunfire erupted on a train that pulled into a station in the Sunset Park neighbourhood in Brooklyn, about a 15-minute ride from Manhattan and predominantly home to Hispanic and Asian communities.
Hourari Benkada, 27, told CNN he was sitting next to the subway shooting suspect on the N train and was shot in the back of his knee while trying to flee.
"I feel shocked, I feel shaky, I don't know if I can ever ride a train," Mr Benkada, a lifelong New Yorker, told CNN after coming out of surgery.
Mr Benkada, a housekeeping manager at the New Yorker Hotel, said he got on the last car of the N train and sat next to a man with a duffel bag who was wearing an MTA vest.
The man then let off a "smoke bomb" and started shooting about 20 seconds after the train took off, Mr Benkada said.
Mr Benkada said he was focused on helping a pregnant woman, who he feared would get hurt as people rushed to the front of the car to avoid the shooter, when he got shot, describing it as "the worst pain of my entire life".
He explained the bullet hit him in the back of his knee and came out the other side.
Doctors told him the bullet grazed his kneecap. He is expected to walk on his own after several weeks on crutches.
Mr Benkada said he heard other people in pain but was unable to see them or the suspect because of the smoke.
Police Commissioner Sewell said the attack was not being investigated as terrorism, but that she was "not ruling out anything." The shooter's motive was unknown.
Authorities gave officers a photo they believed to depict the gunman, and the Arizona licence plate number of a U-Haul truck to look out for, two law enforcement officials said. By early evening, police found a matching, unoccupied U-Haul van in Brooklyn, one of the officials said.
Police were closing off a street about four miles from the shooting scene and clearing nearby businesses while awaiting a bomb squad and the highly specialised emergency services unit.
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Investigators recovered a handgun at the scene, along with multiple smoke devices and other items they are analysing, said the officials, who were not authorised to discuss the investigation and spoke on condition of anonymity.
They said the suspect is believed to have had at least two extended magazines.
Investigators believe the weapon jammed, preventing the suspect from continuing to fire, the officials said.
The federal Bureau of Alcohol, Tobacco, Firearms and Explosives has completed an urgent trace to identify the gun's manufacturer, seller and initial owner.
The attack unnerved a city on guard about a rise in gun violence and the ever-present threat of terrorism. It left some New Yorkers jittery about riding the nation's busiest subway system and prompted officials to increase policing at transportation hubs from Philadelphia to Connecticut.
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The Metropolitan Transportation Authority announced last fall that it had put security cameras in all 472 subway stations citywide, saying they would put criminals on an "express track to justice."
But the cameras apparently malfunctioned in the station where the train arrived, Mayor Eric Adams told WCBS-AM.
One rider's video, shot through a closed door between subway cars, shows a person in a hooded sweatshirt raising an arm and pointing at something as five bangs sound. In another video, smoke and people pour out of a subway car, some limping.
"Someone call 911," a person shouts.
Other video and photos from the scene show people tending to bloodied passengers lying on the platform — some amid what appear to be small puddles of blood — and another person on the floor of a subway car.
Rider Juliana Fonda, a broadcast engineer at WNYC-FM, told its news site Gothamist that passengers from the car behind hers started banging on the connecting door.
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"There was a lot of loud pops, and there was smoke in the other car," she said.
"And people were trying to get in and they couldn't, they were pounding on the door to get into our car."
As police searched for the shooter, Governor Kathy Hochul warned New Yorkers to be vigilant.
"This individual is still on the loose. This person is dangerous," the Democrat said at a news conference just after noon.
"This is an active shooter situation right now in the city of New York."
Fire and police officials had responded to reports of an explosion, but Commissioner Sewell said at the press conference that there were no known explosive devices.
Multiple smoke devices were found on the scene, mayoral spokesperson Fabien Levy said.
After people streamed out of the train, quick-thinking transit workers ushered passengers to another train across the platform for safety, MTA system chief Janno Lieber noted.
High school student John Butsikaris was riding the other train when he saw a conductor urging everyone to get in.
He thought it might be a mundane problem until the next stop, when he heard screams for medical attention and his train was evacuated.
"I'm definitely shook," the 15-year-old told The Associated Press.
"Even though I didn't see what happened, I'm still scared, because it was like a few feet away from me, what happened."
No transit workers were physically hurt, according to their union.
Besides gunshot wounds, the injured riders were treated for smoke inhalation, shrapnel and panic.
In Menlo, Iowa, President Joe Biden praised "the first responders who jumped in action, including civilians, civilians, who didn't hesitate to help their fellow passengers and tried to shield them".
Adams, who is isolating following a positive COVID-19 test on Sunday, said in a video statement that the city "will not allow New Yorkers to be terrorised, even by a single individual."
New York City has faced a spate of shootings and high-profile incidents in recent months, including on the city's subways. One of the most shocking was in January, when a woman was pushed to her death in front of a train by a stranger.
Adams, a Democrat a little over 100 days into his term, has made cracking down on crime — especially on the subways — a focus of his early administration, pledging to send more police officers into stations and platforms for regular patrols. It wasn't immediately clear whether officers were already inside the station when the shootings occurred.
Danny Mastrogiorgio of Brooklyn had just dropped his son off at school when he saw a crush of panicked passengers, some of them wounded, running up the stairway at the nearby 25th Street station. At least two had visible leg injuries, he said.
"It was insane," he told the AP.
"No one knew exactly what was going on."
Allan Lee was running his business, Cafe Nube, when a half-dozen police cars and fire vehicles suddenly converged on the block that contains the 36th Street station.
"Then they started ushering people that were on the block to the adjacent block and then closed off the subway entrance," Mr Lee told the AP.
When he noticed bomb squad officers and dogs, he was certain it was no everyday subway problem.
