A man has been arrested over the shooting that killed a bikie boss's brother in Sydney in May this year.

Comancheros boss Tarek Zahed, 41, and his brother Omar, 39, were gunned down in the foyer of a gym in Auburn on May 10.

Omar died at the scene, while Tarek sustained multiple bullet wounds, including one to the head, but survived.

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Two Audi Q7 cars were found on fire at Berala and Greenacre a short time later.

Detectives yesterday arrested a 22-year-old man at Sydney Domestic terminal at about 10.30pm yesterday.

He was charged with concealing a serious indictable offence.

The man was refused bail and will appear in court today.

The investigation is continuing.

Anybody with information is urged to contact Crime Stoppers or police.