Two people are dead after a six-hour police stand-off in a Sydney industrial estate which ended with the gunman taking his own life.
Tactical response officers swarmed Ingleburn signage business Inline around 10.45am on Monday after three brothers were shot, one fatally, over what's believed to be a business dispute.
The gunman, who was thought to be armed with an assault rifle, holed up in the factory unit as negotiators tried to get him to give himself up.
Nearby local businesses and surrounding streets were sent into lockdown, with police telling people not to go near windows.
Three hostages were released from the factory building in Heald Street just after 5pm and officers then found the gunman's body.
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"(Police) located three persons, factory workers, hiding in that unit," Acting Commander Mark Brett said.
"A further search of that unit located a male deceased.
"It's believed that person died from a self-inflicted gunshot wound."
He would not say when the man died, and said this was now a matter for the homicide squad, though it's understood he may have died several hours before police entered the building.
Police have also not confirmed his identity, though he is believed to be a 33-year-old who some media are naming as Finks bikie gang associate Wayne Williams.
"We have a suspect in mind and that's all I'm prepared to say at this time," Mr Brett said.
The victim of the shooting on Monday morning is believed to be 43-year-old Michael "Mick" Bassal, and the injured men his two brothers.
The surviving brothers are being treated at Liverpool Hospital, where distraught family have gathered.
One of the men required emergency surgery, while the other suffered superficial injuries to his lower body.
A person of interest was arrested earlier in the day at the industrial estate and led away in handcuffs, allegedly for hindering the police operation.
Streets remain shut around the second generation, family-owned business and traffic is being diverted away from the area, which is still being treated as a crime scene.
Staff at neighbouring businesses had been told to stay in their factory warehouses, but police allowed a number of cars to leave the factories mid-afternoon before the end of the stand-off.
"Police told us not to go near windows," an employee at one local business told AAP.
Another said the area was usually quiet and without incidents.
"I'd never really noticed the business before today," he said.
"Nothing happens here."
* For support and information about suicide prevention, call Lifeline on 13 11 14
