Fred Guttenberg, the father of a slain Parkland student, said on Twitter that he tried to approach Supreme Court nominee Brett Kavanaugh only for the judge to ignore him.
The incident occurred as the Senate Judiciary Committee took a recess shortly after noon Tuesday.
"Just walked up to Judge Kavanaugh as morning session ended. Put out my hand to introduce myself as Jaime Guttenberg's dad. He pulled his hand back, turned his back to me and walked away. I guess he did not want to deal with the reality of gun violence," Guttenberg tweeted.
White House deputy press secretary Raj Shah addressed the moment on Twitter, saying, "As Judge Kavanaugh left for his lunch break, an unidentified individual approached him. Before the Judge was able to shake his hand, security had intervened."
A source familiar with the encounter said Kavanaugh did not know who Guttenberg was and that security intervened to end the exchange before there could even be a handshake. The source said Kavanaugh's security detail quickly stepped in because they did not know who the person was.
CNN has reviewed the video that shows Guttenberg holding out his hand to Kavanaugh with the judge seen listening to Guttenberg, expressionless, before turning away as security intervenes.
Shah posted a video of the moment and said it "clearly shows security intervened" when Kavanaugh was approached.
Guttenberg disputed Shah's account, replying, "Incorrect. I was here all day and introduced by Senator Feinstein. No security involved. He turned and walked away."
Sen. Dianne Feinstein, the top Democrat on the Judiciary panel, introduced Guttenberg and several other advocates during her opening statement.
Jaime Guttenberg was 14 when she died in the shooting at Marjory Stoneman Douglas High School in Parkland, Florida, earlier this year.