Latrez Cummings, 19, James Davis, 24, and Wonzey Saffold, 30, entered guilty pleas Thursday to assault. They had been charged with attempted murder and could have received 25-year sentences if convicted.
Bruce Wimbush Jr., 18, pleaded guilty to the same charge Monday. A 16-year-old who prosecutors said was the first to hit Steve Utash, 54, entered a guilty plea Wednesday.
Ray Paige, Saffold's lawyer, said Wimbush and the teenager had agreed to testify against the other three.
Utash spent days in an induced coma and weeks in the hospital after the attack April 2. He was more severely injured than the 10-year-old boy he struck, who had a broken leg.
Police said Utash was not at fault in the accident and behaved properly, stopping and getting out of his truck to see if the boy needed assistance.
While there were suggestions the attack was racially motivated because Utash, who lives in Clinton Township in the Detroit suburbs, is white and his alleged assailants are black, Paige said that was untrue.
"If he had been a black man, they would have done the same thing," Paige said.
Paige said his client is likely to get six years in prison when he is sentenced in July.