Police have hailed the actions of staff at a Sydney law firm after they helped detain a gunman on Wednesday afternoon.

One man was shot on a street near major court complexes in central Sydney, while another was arrested nearby.

Police said “five or six brave employees” at a law firm assisted detaining the alleged gunman and there was no ongoing threat after officers arrested the man.  

Emergency services were called about 12.50pm on Wednesday to a building on Castlereagh St following reports a person had been shot.

A man aged 77 was found at the scene suffering a gunshot wound, police said.

He was taken to St Vincent’s Hospital for treatment.

Workers inside the law firm reportedly helped restrain the alleged shooter, belived to be aged 79, and gave the wounded man first aid until ambulance crews arrived.

“At the scene we found more one male offender being held down by staff members on the premises. He was arrested,” Detective Inspector David El-Badawi said.

“We also found a victim in his late 70s with a gunshot wound to his groin. He was treated by paramedics,” he said.

Workers inside the law firm helped restrain the alleged shooter and gave the victim first aid until ambulance crews arrived.

The relationship between the two men is so far unknown, but El-Badawi said at this stage it was not being treated as a gang-related shooting.

“This is an isolated shooting, we don’t believe it is connected to any outlawed motorcycle gangs or any gang warfare,” he said.

“The city is safe, within three minutes police attended, there was at least 40 police on scene.”

– with AAP