Vulic was allegedly carrying a loaded M1 carbine semi-automatic rifle with the shoulder butt removed and a loaded CZ45 handgun at the time of the shooting.

Officers were on the scene in three minutes, finding five to six workers holding the alleged gunman on the ground, Detective Inspector David El-Badawi said after the arrest.

"The people inside the office were very brave," he told reporters on Wednesday.

"They restrained the offender until police arrived."

Vulic's barrister Ken Buckman briefly appeared at Downing Centre Local Court on Thursday, when he requested medical checks to be carried out while the 79-year-old was in custody.

No application for bail was made and the matter will next come before the court on May 2.

The relationship between Vulic and Mr Cooney was yet to be deduced but police had ruled out links to outlaw motorcycle gangs, Det Insp El-Badawi said.

The one bullet fired from the weapon entered the man's groin, but the victim was in a stable condition when paramedics arrived.

"It wasn't a graze, but when we got on scene, it was not actively bleeding," NSW Ambulance inspector Dominic Wong said.

"I do believe there was first aid rendered by the people in the premises and that obviously assisted with his treatment."

The 77-year-old was taken to St Vincent's Hospital in a stable condition.

Vulic faces seven charges including shooting with intent to murder, two counts of possessing a loaded firearm endangering life in a non-public place and two counts of possessing an unauthorised prohibited firearm.

He also faces two counts of acquiring a firearm in contravention of a firearms prohibition order.