Former Vice President Joe Biden said he wasn’t expecting Senator Kamala Harris to attack him on his busing record during the first 2020 Democratic debate last month.

“I was prepared for them to come after me,” Biden told CNN’s Chris Cuomo on Thursday during a campaign stop in Iowa. “But I wasn’t prepared for the person coming at me the way she came at me.”

The former vice president added that Harris “knew Beau, she knows me,” referring to Biden’s son, Beau, who died from brain cancer in 2015.

Since criticizing Biden during the debate, Harris has struggled to explain her own position on busing. She told Biden on stage that the “federal government must step in” when there is a failure of states to integrate public schools. But this week Harris appeared to change positions, saying busing should be “considered” by school districts and not mandated.

During his CNN interview, Biden argued that his past voting record on busing and other issues regarding race have been taken completely “out of context” during the 2020 race. He defended his support for voluntary busing and busing when a court ruled that a specific legislative action prevented black students from attending a school. He also mentioned his time as a public defender, saying he fought for low-income housing and eliminating the breadline.

“Why didn’t you fight it like this in the debate?” Cuomo asked. Biden said that he only had 30 seconds on stage to make a rebuttal.

“What happens most in a debate Mr. Vice President? People blow their time queue. You’re the only person I’ve ever seen on a debate stage say ‘I’m out of time,'” Cuomo said. Biden responded that he didn’t want to get into a “scrum” in front of voters.

In what was one of the most heated exchanges of the first Democratic primary debate, Harris came after the former vice president for his record on race. Biden had recently been under fire for touting his ability to work with two segregationist senators who were strongly opposed to the civil rights movement.

“I do not believe you are a racist. And I agree with you when you commit yourself to the importance of finding common ground,” Harris said to Biden before adding that his comment about the segregationist senators was “personal and it was actually very hurtful.”

Harris continued, adding that Biden worked with the two senators to oppose busing for black students.

“There was a little girl in California who was part of the second class to integrate her public school and she was bused to school every day. And that little girl was me,” Harris said. “So I will tell you on this subject, it cannot be an intellectual debate among Democrats. We have to take it seriously.”

When it was Biden’s turn to respond, he called Harris’ remarks a “mischaracterization of my position across the board.” But he ultimately relented, saying: “My time’s up, I’m sorry.”