A suburb in Sydney's west was thrown into lockdown overnight for several hours as police searched for a gunman.

The search started from a simple traffic infringement and the fugitive remained on the run this afternoon.

The shooter, wearing high-vis, was last spotted in Guildford.

"A vehicle with irregular number plates committed a right-hand turn against traffic signs," Chief Inspector Rick Agius said.

The vehicle was a ute initially seen in South Wentworthville, before taking authorities on a nine-kilometre chase and eventually being pinned by police.

But the driver made a run for it, firing five shots into the air.

"The male in my opinion is totally irresponsible and stupid in his actions by discharging a firearm in a public place," Agius said.

"We're very lucky that no one was injured or killed."

Anyone with information can contact Crime Stopper

After a six hour manhunt and a search of the vehicle, authorities are no closer to figuring out who this man is and are hoping a member of the public can identify him.