This wasn’t a stutter — he just flipped out.

After a campaign event in Mason City, Iowa on Wednesday, Joe Biden was being pursued by CBS reporter Ed O’Keefe, who wanted to know about Biden’s recent kerfuffle with Bernie Sanders.

WATCH: After a campaign event in Mason City, Iowa, @joebiden reacts to @edokeefe's question about his ongoing feud with @berniesanders: "Calm down, it's okay." https://t.co/a2hmMbnjnf pic.twitter.com/ymOMWRR2zP

— CBS News (@CBSNews) January 22, 2020

“Yesterday, you said you accepted Bernie’s apology, now you’re attacking him. Why are you doing that? Why wasn’t this apology enough, Mr. Vice President?”

“Why attack Sanders?” he wondered.

Biden stopped, turned around as he was about to disappear behind the security curtain and blurted out, “Why why why why why why why?!?

“You’re getting nervous, man! Calm down, it’s okay,” Biden said, stroking the reporter’s chest.” He apologized for saying that I was corrupt. He didn’t say anything about whether or not I was telling the truth about Social Security.”

Biden then thumped O’Keefe on the chest and walked away.

Sanders has been criticizing Biden over his past statements about Social Security, which Biden claims aren’t true.

But here’s Sanders’ latest ad:

Let’s be honest, Joe. One of us fought for decades to cut Social Security, and one of us didn’t. But don’t take it from me. Take it from you. pic.twitter.com/qh7qb1Hmcl

— Bernie Sanders (@BernieSanders) January 22, 2020