A 79-year-old man has been charged over a shooting in a Sydney city-centre office that wounded another septuagenarian.

The victim, 77, was injured in an office block about 12.50pm on Wednesday on Castlereagh Street, a stone’s throw from a major Sydney court complex and home to several law firms.

Police 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.

“The people inside the office were very brave,” he told reporters.

“They restrained the offender until police arrived.”

The relationship between the two men was yet to be deduced but police had ruled out any links to outlaw motorcycle gangs, Det Insp El-Badawi said.

He declined to reveal whether the scene, on the ninth floor of the office block, was a legal firm.

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.

Police said early on Thursday they had seized a rifle and ammunition following a search of the 79-year-old man’s belongings.

He faces several charges including shooting with intent to murder, possessing a loaded firearm endangering life in a non-public place and possessing an unauthorised prohibited firearm.

The suspect was refused bail to appear at Downing Centre Local Court on Thursday.

-AAP