Police say the alleged gunman of a Sydney shooting did not have a firearms licence, as detectives probe for a motive behind the attack that left one man in a critical condition and dozens more injured.

Croydon Park, in Sydney’s inner west, was plunged into lockdown just after 7:45pm on Sunday following reports of an active shooter.

Locals ducked for cover as the alleged gunman fired shots from the window of a unit above a business on Georges River Road, with bullets striking vehicles and a nearby bus shelter.

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Acting Superintendent Stephen Parry said between 50 to 100 shots were fired “indiscriminately” at passers-by over a two-hour period.

One man, aged in his 50s, was shot in the neck and chest. He was taken to hospital in a critical condition and underwent emergency surgery.

Croydon Park is a multicultural suburb with mixed-residential housing that is popular with young families.

The road where the shooting occurred has a series of eateries and fast food places, and is nearby a school and church.

At least 16 people suffered minor injuries, with two men taken to Royal Prince Alfred Hospital for treatment.

Among the injuries were facial cuts from shattered glass and shrapnel, while some patients were treated for shock, NSW Ambulance said.

Shooting something like ‘a movie’A picture of unit on top of a business with shattered glass

The shopping strip in Croydon Park has become a crime scene. (ABC News: Timothy Ailwood)

Pictures from the scene showed cars with shattered windows.

A succession of bangs rang out just after 9pm and witnesses said they believed there were flash grenades.

A taxi driver, who was also an eyewitness, said he thought someone had let off firecrackers.

“As I was driving by I just heard a ‘bang, bang, bang’ on the left shoulder of the taxi,” he said.

a man in a white shirt holding an energy drink

A taxi driver told ABC News he thought someone had let off firecrackers. (ABC News)

“I looked and I saw a couple of holes through the window on the passenger side … I didn’t realise there was a hole on the roof as well.

“I smelt the gunpowder but I assumed because it was grand final night it was somebody throwing firecrackers or something.

“I’m just in shock … it feels like it’s a movie.”

glass from the window on the passenger's side of a car is shattered

Glass from the window of a car was left shattered.  (ABC News: Timothy Ailwood)

Another resident was working from his office when he heard glass shattering.

“Some guy’s windshield blew up and then the bus stop glass had shattered,” he said.

“Bullets were just hitting stuff so we just ran back into the office.

“From there we just stayed on the floor and called the police.

“And then all night we’re just hearing volleys of gunshots back and forth until it kind of relieved itself and we could hear the police yelling at the guy, ‘Put your weapon down’ and all that kind of stuff.”

A police car that was struck was seen being towed away on Monday morning.

A police car towed from the scene of a shooting in Sydney's inner-west

A police car was towed away from the scene of a shooting in Sydney’s inner west on Monday morning. (ABC News: Timothy Ailwood)

Man arrested and weapons seized

A 60-year-old man was arrested at about 9:30pm at a unit above a business on Georges River Road where the shots were believed to have came from.

Police located and seized several firearms, including a long-arm high-calibre rifle.

Acting Commissioner Trent King said the shooting did not appear to be drug or alcohol-related.

“In terms of motive we simply don’t know at the moment,” he said.

Croydon Park shooting

Police secured the premises and the scene. (ABC News: Tony Ibrahim)

Acting Commissioner King said the man did not have a gun licence and police are probing whether the gun was legally owned.

The 60-year-old was taken to hospital after sustaining injuries during the arrest and is currently under police guard.

A crime scene was established and the lockdown has since been lifted.

Forensic officers were seen scouring for evidence on Monday morning, with inquiries ongoing.