The New York Republican lost his temper during an interview with NY1 News television immediately after President Barack Obama's State of the Union address yesterday.
"He called to apologize. He said that he overreacted," reporter Michael Scotto, the target of Grimm's outburst, said on NY1.
"I accepted his apology and I think we're going to move on from here."
The confrontation unfolded in an unlikely locale: a television stand-up spot in the rotunda of the Cannon House Office Building in the US Capitol complex.
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"Let me be clear to you, you ever do that to me again I'll throw you off this f***ing balcony," Grimm said in video broadcast by the cable station, which confirmed the comments.
Pressed by Scotto why the question was off limits, Grimm responded: "You're not man enough. I'll break you in half. Like a boy."
After NY1 News demanded an apology and New York Mayor Bill de Blasio reportedly described Grimm's behavior as "absolutely inappropriate," Grimm sang a different tune today.
"I was wrong. I shouldn't have allowed my emotions to get the better of me and lose my cool," Grimm said in a new statement, adding that he will be inviting Scotto to lunch soon.
Earlier, station political director Bob Hardt said it was "extremely disturbing" that a lawmaker would issue such threats.
Grimm, a former US Marine and FBI special agent, "verbally took the reporter to task... Because I expect a certain level of professionalism and respect," he said.