Detroit driver Steve Utash beaten by mob after he accidentally hit 10-year-old David Harris

The 54-year-old's daughter said that the family is organising a fundraiser to pay for the tree trimmer's hospital fees

Steve Utash with his wife Starr Utash, taken in 2012. (Facebook/Starr Utash)

Police in the US city of Detroit are searching for attackers that severely beat a man when he stopped to check on a 10-year-old boy he had mistakenly knocked down with his car on Wednesday afternoon.

54-year-old tree trimmer Steve Utash remains in a critical condition at St John Hospital and Medical Centre, Detroit, where his family are keeping a vigil, according to the Detroit Free Press.

He was not at fault when he accidentally hit David Harris, said Detroit police Sergeant Michael Woody.

“A preliminary investigation shows the kid stepped off the curb in front of him,” Woody said. “No way he could have stopped in time.”

Security footage seen by CBS Detroit from a petrol station near the scene, shows Harris run into oncoming traffic and being hit by Utash's pickup truck.

The tree trimmer then stops to check on the boy, and is set on by the attackers.

David’s godfather, James Duston Jr., told the newspaper that the boy is also still in hospital after he suffered abrasions on his knee, swelling on his lip, and is having problems with one of his feet. He is expected to recover from his injuries.

Utash's daughter, 20-year-old Felicia Utash, said her father does not have health insurance and the family plans to set up a fund-raiser to cover his hospital bill.

Cars enter local business at the scene of an attack on Wednesday in Detroit. (AP Photo/Detroit News, Clarence Tabb Jr)

Marked and unmarked police officers are now searching for the culprits around the Morang and Balfour areas where the accident occurred.

The boy’s uncle, 21-year-old Desmond Key, witnessed the event and said that he and his friends were on their way to the local shop when they saw the boy being hit by Utash's pickup truck.

One of the alleged culprits then raced back to David’s home and alerted the family to the accident.

"I heard that he ran out in the street," Key said. "When I showed up my nephew was on the ground screaming."

Utash was then being beaten in the driveway of a petrol station by around six or seven attackers, said Key.

“The guy [Utash] definitely was trying to fight back, but it was too many guys,” Key said. “When he finally had enough of trying to fight back he just fell to the ground. When he fell to the ground they kicked him a couple of times and then they left him alone.”

“We don’t know those people that did that to that guy. Our main focus is on David,” he said. “We weren’t cheering it on. We weren’t rooting for it.”