LONGMONT, Colo. -- A man on probation for accidentally backing a car over a 2-year-old boy in March could face a careless-driving charge for backing over the boy's 4-year-old brother.

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Driver Stumped After Running Over Another Child

Ronald Frederick Daniel, 53, ran over Ulisses Castillo-Garcia's torso on Friday in the same dirt driveway with the same Acura sedan he was driving when he struck the boy's younger brother, according to police.

"They don't know if he's going to walk again," Maribel Castillo, the older boy's aunt said of Ulisses' injuries.

A number listed for Daniel at the address where the accident happened was disconnected Sunday.

Officer Dave Yocum said drugs or alcohol were not suspected, and added Daniel was under investigation for careless driving.

"Apparently, the rear wheel went right over the child's torso," he said.

Daniel told Denver TV station KMGH Monday that he has no idea how the second accident happened.

Daniel was sentenced to a year probation after pleading guilty Sept. 27 to driving while ability impaired for backing up and running over the younger boy on March 25. The younger boy, Edel Castillo, suffered minor injuries.

Daniel admitted having smoked cocaine days before the March accident but a urinalysis showed Daniel did not have cocaine in his system at the time of the accident.

According to police, Daniel is the boyfriend of Minerva Garcia, the boys' mother.