WATCH: Firefighter saves four-year-old who fell from back of moving bus

A firefighter watched in horror as a child’s body rolled towards his car, moments after she fell from the back of a moving bus.

It was a case of 'right place, right time' for the volunteer, Ryan Ciampoli, who immediately rushed to help the child.

The scene was caught on Mr Ciampoli's dash cam, as he was driving behind the bus.

The girl was seen hanging from the bus door before she fell on to the road. Photo: Ryan Ciampoli.

He saw the girl open the door and fall out of the bus, on to the road.

The child's body could be seen rolling towards his car.

"I saw it happening, and it blew my mind, it was like I wasn't even seeing what I was seeing," Mr Ciampoli told KHBS-TV.

The bus was driving down a busy highway in Arkansas when the back door opened and the girl appears to be hanging from it.

The girl then fell from the bus as it continued to drive away. It's likely the driver did not notice the child fall.

"Obviously, you want to leave her there, if she’s not in danger, but obviously, we're in the middle of a state highway, so I couldn't leave her just lying there," Mr Ciampoli said.

Ryan Ciampoli rushed to help the child, after seeing her fall from the bus. Photo: Ryan Ciampoli.

Mr Ciampoli said she was unconscious at first, but started to wake up when he approached her.

He carried her off the road and laid her on a truck bed in a nearby parking lot.

He got to work by keeping her conscious and checking her vitals.

"The shock kicked in her little body and she started kicking and screaming and asking "where's my mummy," Mr Ciampoli said.

The four-year-old’s mother has said she has a broken jaw and will need surgery.

She is expected to be OK.