An ex-girlfriend of Darrell Brooks said she was "mortified" by Sunday's attack in Waukesha.
She told the New York Post that she was "embarrassed" Brooks is the father of her child.
Brooks is charged with five homicides after a vehicle rampage at the city's Christmas parade.
An ex-girlfriend of the man suspected of killing six people and injuring 58 more in a car rampage in Wisconsin says she is "mortified" and can't sleep since the event, she told the New York Post.
Darrell Brooks, 38, was charged Tuesday with five counts of intentional homicide after the killings in the city of Waukesha.
Police say he was the driver of a red Ford Escape that plowed through crowds of people celebrating Waukesha's Christmas parade on Sunday.
A further charge is expected next week after eight-year-old Jackson Sparks died of his injuries. A cash bond of $5 million was set for Brooks on Tuesday, court records show.
An ex-girlfriend and the mother of one of his children, whom the Post did not name as she feared for her safety, told the paper her reaction when she saw Brooks in the news.
"When I saw his picture online, I was like, 'What the fuck?,'" she is reported as saying.
Brooks did not stick around long as a father, she said, leaving her to raise their boy after three months. According to the paper, she lives in southern Milwaukee.
At the time of Sunday's horrific events, Brooks was on bail over a charge of running over an ex-girlfriend in his car just three weeks earlier. According to the Post, this is a different ex.
The Milwaukee County District Attorney's Office said after Sunday's events that the $1,000 bail he had been granted was "inappropriately low."
The ex claimed that Brooks' mother, Dawn Brooks, desperately regrets covering his bail.
"She's wrecked that people were killed as a result and she's like, 'I'm blaming myself, because had I not bailed him out, this wouldn't have happened,'" the ex is reported as saying.
The ex said she was already "embarrassed" that Brooks is the father of her child, "because he wasn't taking care of him," she told the paper. "What do you think I am now? Mortified."
Saying she wishes she could replace her son's father with another person, she added that she is "sickened by it, obviously devastated, can't sleep," the paper reported.
"I've been donating and saying prayers and doing everything that I can."