Police have charged an officer who fired two shots at a car carrying five people.

Senior Constable Niko Westergerling was charged with two counts of discharging a firearm in a manner that endangers others.

It is alleged he fired two shots at a car carrying five people, including a 3-year-old boy, as it sped away from a traffic stop in Nollamara on Monday afternoon.

Senior police say an investigation has found the shooting was not justified.

Police have spoken to the passengers who were in the car and say they are not facing any charges, although a search continues for the female driver.

It is understood an outstanding bench warrant could be preventing her from coming foward but police are trying to make contact with her through the Aboriginal Legal Service.

Hung out to dry

The WA Police Union president Russell Armstrong says constable Westergerling has been hung out to dry by the force.

"We are looking after this officer; he's innocent until proven guilty," he said.

"We'll provide legal support for him but I am amazed at the comments that were made and I hope if he does go to trial he will receive a fair trial."

Mr Armstrong says the union will support the officer as the process works its way through.

"Look, I'd say they've done a thorough investigation but certainly he's been hung out to dry but we'll just wait and see what the process happens; we'll let that go through," he said.

The officer has been stood down from duties.

Constable Westergerling has been summonsed to appear in the Perth Magistrates Court on December 16.

The maximum penalty is three years jail or a fine of up to $12,000.