A baby boy has avoided serious injury after a man stole and crashed a family car as the 11-month-old slept in his car seat on Sunday night.

The boy had been asleep in the car on Denien Street, Willagee while his parents inspected the construction of their new home just metres from the vehicle.

Moments later, a man, who had been walking past with a woman, stole the vehicle.

Neighbour Iris, who did not want her surname published, said it had been a hot day and the boy’s parents left the air-conditioner of the car running while he slept.

“He left the car there, just for a second and all of a sudden a couple came by…they weren’t even there long,” she said.

“By the time they saw them walk by, when they turned around their car was off…it just happened so quick.”

The boy’s father and brother jumped onto the car bonnet and chased the vehicle down the street before it crashed into a Holden Commodore on nearby Wheyland Street and the man fled.

“I’ve lived here for 60 years and nothing (like this) has happened,” Iris said. “It’s frightening for them and it’s a shame because he’s such a nice guy, working hard building his own house.”

The boy sustained a cut lip, but escaped without serious injury.

A St John Ambulance spokesman said an ambulance was not required and paramedics had not treated anyone involved in the crash.

Police media confirmed they were still looking for the offender.

Debris, including the stolen car’s front bumper, remained on the corner of Wheyland Street and broken tail car lights were found shattered outside the Denien Street home this morning.