NY1 officials say they are alarmed and disappointed by Grimm's behavior and demanded a full apology, which Grimm eventually offered.
Initially, however, the Staten Island Republican stood his ground, refusing to say he was sorry and calling the question by reporter Michael Scotto a cheap shot.
The confrontation began when Scotto asked Grimm about a Justice Department investigation into his campaign finances. After cutting the interview short, Grimm told Scotto, "Let me be clear. You ever do that to me again, I'll throw you off this (expletive) balcony."
"You're not man enough," he told Scotto. "I'll break you in half like a boy."
Grimm later issued a statement saying he was "extremely annoyed" with Scotto and doubted he was the "first member of Congress to tell off a reporter."
"I was extremely annoyed because I was doing NY1 a favor by rushing to do their interview first in lieu of several other requests," the statement read. "The reporter knew that I was in a hurry and was only there to comment on the State of the Union, but insisted on taking a disrespectful and cheap shot at the end of the interview, because I did not have time to speak off-topic. I verbally took the reporter to task and told him off, because I expect a certain level of professionalism and respect, especially when I go out of my way to do that reporter a favor. I doubt that I am the first Member of Congress to tell off a reporter, and I am sure I won't be the last."
Just after 11 a.m., Scotto tweeted: "@repmichaelgrimm called to apologize. He said he "overreacted." I accepted his apology."
Grimm released another statement after issuing the apology, saying "I was wrong. I shouldn't have allowed my emotions to get the better of me and lose my cool. I have apologized to Michael Scotto, which he graciously accepted, and will be scheduling a lunch soon. In the weeks and months ahead I'll be working hard for my constituents on issues like flood insurance that is so desperately needed in my district post Sandy."
Grimm, a Marine and one-time undercover FBI agent, was first elected to Congress in 2010. He is New York City's only Republican congressman, representing all of Staten Island and part of Brooklyn.
Earlier this month, the FBI arrested Grimm's former girlfriend on charges she illegally funneled thousands of dollars into his campaign. Grimm also faces an ongoing federal investigation into allegations that he or his campaign illegally solicited money from foreign donors.
Grimm has not been charged with any crime and has denied all wrongdoing.