Darrell Brooks, 38, was charged on Tuesday with five counts of intentional homicide after he allegedly drove his car into a crowd watching a Christmas parade on Sunday. Six people were killed and more than 50 others injured.
A former girlfriend spoke with The New York Post, telling the outlet she was "mortified" by the violent event and could not sleep.
The woman, who was not named by the paper, said she and her son have had very little contact with Mr Brooks in the past 20 years. She claims he walked out on them when her child was three months old.
“He disappeared when my son was almost three months old,” she said. “I’ve done all of this on my own, raised my child by myself.”
She told the paper that when she saw his photo online, she thought "what the f***?"
“I was embarrassed enough to have him as the father of my child beforehand, because he wasn’t taking care of him,” she said. “What do you think I am now? Mortified.”
She said she was "sickened" by his actions, and wished she could replace him as the father of her child. She said she has lost sleep over the incident and has been donating and saying prayers for the victims.
The ex also revealed that Mr Brooks' mother, Dawn Woods, was wracked with guilt over paying the $1,000 bail that allowed her son to leave custody days before he allegedly drove into the crowd.
“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 said.
Mr Brooks was arrested initially after he was accused of punching the mother of his child and intentionally hitting her with his car on 2 November. Milwaukee prosecutors called the bond "inappropriately low" considering his actions.
His ex said his mother was always trying to push him to be a better man, and never condoned his allegedly violent and illegal acts.
“She’s always condemned everything that he’s done … even weed possession, she’s never condoned,” she said. “She’s always been very resolute on, ‘You need to do better. You need to do right. This is not how I raised you.’”