The policeman who fired two shots at a speeding car during an operation targeting hoons was alone and in plain clothes when he pulled the trigger.

Assistant Commissioner Luke Cornelius said the constable feared for his life when he shot at the car as the driver tried to run him over in Melbourne’s south-east on Tuesday night.

The officer, who missed the car with both shots, had been a plain clothes ‘‘spotter’’ during an operation in Carrum Downs to smash a hoon driving ring that had terrorised residents between Dandenong and Frankston in recent weeks.

More than 100 cars had gathered for street drag races when police swooped.