A man has been charged after allegedly mowing into six stationary cars, killing a boy and seriously injuring his mum and younger sister before fleeing the scene.

Labourer John Pagakis, 34, was allegedly speeding when his Holden Commodore became airborne and crashed into stationary vehicles when exiting the M2 in Baulkham Hills, north-west Sydney, at 7pm on Saturday.

The boy, aged 12, was pronounced dead at the scene. His mother, 36, and younger sister, aged 5, were also in the Holden Captiva when Pagakis allegedly rammed his car into them. They are in a critical condition.

The boy’s 38 year-old father was in the driver’s seat but was not injured. “My son, my son,” he screamed.

NSW Fire and Rescue services rushed to the scene. Inspector Kernin Lambert described an “absolutely horrific” scene where five people had to be cut out of their vehicles.

Mr Pagakis got out of his mangled car and fled the scene of the accident on foot. He was arrested eight hours later at his mother’s northern beaches home. Dimitra Pagakis, the mother, described the incident as a “nightmare.”