Ronald Rowe testified that he recently visited the shooting site and said, "What I saw made me ashamed."

The testimony from Rowe amounted to the most detailed catalogue to date of law enforcement failings and miscommunications, with the Secret Service boss accepting blame for his own agency's mistakes while also criticizing local law enforcement for not sharing information that a gunman, later identified as 20-year-old Thomas Matthew Crooks, had been spotted on a roof near the rally site in the minutes before the July 13 shooting in Butler, Pennsylvania.

That information, he said, had been kept "siloed" among the local officers on the scene.

"It is troubling to me that we did not get that information as quickly as we should have," Rowe said. "We didn't know that there was this incident going on."

The FBI, meanwhile, disclosed new details about Crooks, with Deputy Director Paul Abbate saying a social media account believed to be associated with the gunman suspected in the assassination attempt espoused political violence and included antisemitic and anti-immigrant sentiment. The posts were from the 2019 and 2020 timeframe, when Crooks would have been in high school.

Rowe became acting director of the Secret Service last week after Kimberly Cheatle resigned in the aftermath of a House hearing in which she was berated by lawmakers of both major political parties and failed to answer specific questions about the communication failures preceding the Trump rally shooting.

Sen. Lindsey Graham, the top Republican on the Senate Judiciary Committee, said if something like this happened in the military, "a lot of people would be fired. And if a lot of people are not fired, the system failed yet again."

He added: "Nothing's going to change until somebody loses their job."

The hearing came a day after the FBI released new details about its investigation into the shooting, revealing that the gunman had looked online for information about mass shootings, power plants, improvised explosive devices and the May assassination attempt of the Slovakian prime minister.

The FBI also said that Trump, the 2024 Republican presidential nominee, has agreed to be interviewed by agents as a crime victim. The bureau said last week that the former president had been struck in the ear by a bullet or a bullet fragment. Trump, who appeared at events over the next few days with a bandage on his right ear, said he expects the interview to take place on Thursday.

Most of the questions Tuesday were expected to be directed at Rowe as lawmakers demand answers about how Crooks was able to get so close to Trump. Investigators believe Crooks fired eight shots in Trump's direction from an AR-style rifle after scaling the roof of a building of some 135 meters (147 yards) from where Trump was speaking.

One rallygoer was killed, and two others were injured. Crooks was shot dead by a Secret Service counter-sniper.

At Cheatle's hearing last week, she said the Secret Service had "failed" in its mission to protect Trump. She called the attempt on Trump's life the Secret Service's "most significant operational failure" in decades and vowed to "move heaven and earth" to get to the bottom of what went wrong and make sure there's no repeat of it.

Cheatle acknowledged that the Secret Service was told about a suspicious person two to five times before the shooting at the rally. She also revealed that the roof from which Crooks opened fire had been identified as a potential vulnerability days before the rally.

Cheatle said she apologized to Trump in a phone call after the assassination attempt.

In a Monday night interview on Fox News Channel, Trump defended the Secret Service agents who protected him from the shooting but said that someone should have been on the roof with Crooks and that there should have been better communication with local police.

"They didn't speak to each other," he said.

He praised the sniper who killed Crooks with what he said was an amazing shot but noted: "It would have been good if it was nine seconds sooner."