Democratic front-runner Joe Biden freaked out at a reporter Wednesday after a campaign event in Mason City, Iowa, after he was grilled about his ongoing feud with Bernie Sanders.

The former veep was leaving the event when CBS reporter Ed O’Keefe peppered him with questions about his ongoing criticism of the Vermont senator in an exchange caught on video.

“Yesterday, yesterday, you said you accepted Bernie’s apology. Now you’re attacking him. Why are you doing that? Why wasn’t his apology enough, Mr. Vice President? Why attack Sanders?” a tailing O’Keefe repeated, until Biden stopped in his tracks, whirled around and got in O’Keefe’s face, eyes bulging.

“Why, why, why, why, why, why, why! You’re getting nervous, man. Calm down! It’s OK!” he shouted, placing his palms on O’Keefe’s chest as he then tried to explain.

“He apologized for saying that I was corrupt,” a calmer Biden said.

“He didn’t mention anything about whether or not I was telling the truth about Social Security,” he added, as O’Keefe smiled nervously.

Biden then gave the reporter a gentle left-hand fist bump before turning and continuing on his way.

Biden earlier sought to ease tensions with Sanders after the two candidates exchanged several volleys over Social Security and other matters, noting that Sanders had apologized to him after one of his supporters wrote that the former veep has a “corruption” problem.

“Sometimes campaign staff gets a little ahead of the candidate,” Biden said, later adding, “I accept his apology, and I hope we can argue on the facts.”

But he still angrily disputed that he backed cutting Social Security.