Donald Trump Jr.: 'How Did Someone Get That Close?'

Donald Trump Jr. said the biggest question he wants answered regarding the assassination attempt on his father, former President Donald Trump, is, "How did someone get that close for that long?"

During an interview with Axios on Tuesday, Trump Jr. said a "serious breach" must have occurred on Saturday that led to the shooting during his campaign rally in Butler, Pennsylvania.

"Having had a Secret Service detail," Trump Jr. said, he doesn't understand how the gunman got on the rooftop of the building near his father's event "without a serious breach of something."

"A guy does not get on a rooftop with a rifle where there's people, and now I've seen the videos for five minutes saying, 'There's a guy on a rooftop with a gun,'" he said.

"It literally doesn't happen. I've shot with these guys; I came from a competitive shooting background. ... That doesn't happen without a serious breach of something."

After the shooting that grazed the former president and killed a former fire chief, Trump Jr. said his father was "a bada**" and said he "could not have been more proud of him under those circumstances."

Secret Service Director Kimberly Cheatle is slated to testify before the House Oversight Committee on Monday, as Capitol Hill lawmakers seek to understand how 20-year-old Thomas Matthew Crooks was able to access a rooftop within firing range of Donald Trump's rally.

"The United States Secret Service has a no-fail mission, yet it failed on Saturday when a madman attempted to assassinate President Trump, killed an innocent victim, and harmed others," Oversight Committee Chair James Comer, R-Ky., said in a statement. "We are grateful to the brave Secret Service agents who acted quickly to protect President Trump after shots were fired and the American patriots who sought to help victims, but questions remain about how a rooftop within proximity to President Trump was left unsecure.

"Americans demand answers from Director Kimberly Cheatle about these security lapses and how we can prevent this from happening again."