Acting Secret Service director grilled about Trump assassination attempt

Acting Secret Service Director Ronald Rowe and FBI Deputy Director Paul Abbate are testifying Tuesday on the assassination attempt against Donald Trump at his rally in Butler, Pennsylvania, earlier this month.

The two officials are facing a grilling from lawmakers on security arrangements at the site and the status of ongoing investigations into what occurred leading up to July 13, when a gunman fired on the crowd, injuring Trump and two others and killing Corey Comperatore.

Rowe told lawmakers he was "ashamed" of the protection failures that day and said he visited the site of the shooting as one of his first acts as acting director.

"I went to the roof of the AGR building where the assailant fired shots and laid in a prone position to evaluate his line of sight. What I saw made me ashamed," Rowe said in his opening statement. "As a career law enforcement officer, and a 25-year veteran with the Secret Service, I cannot defend why that roof was not better secured."

"To prevent similar lapses from occurring in the future, I directed our personnel to ensure every event site security plan is thoroughly vetted by multiple experienced supervisors before it is implemented," he added. "It is clear to me that other protective enhancements could have strengthened our security at the Butler event site."

Here are some key moments from the hearing.

Secret Service had no knowledge of gunman on roof until shots fired

Rowe, who took over as the head of the Secret Service after former director Kim Cheatle's resignation earlier this month , testified that Trump's security detail didn't have "any knowledge" there was an attacker on the roof with a gun prior to shots ringing out.

"It is my understanding those personnel were not aware that the assailant had a firearm until they heard gunshots," he said. "Prior to that, they were operating with the knowledge that local law enforcement was working on issue of a suspicious individual prior to the shots being fired."

In dramatic fashion, he also displayed pictures of where the local sniper team was supposed to be posted and showed images of his agents re-enacting the shooter's position.

Rowe also said if they had "more information" about the 30 seconds between finding out the shooter had a gun on the roof and him opening fire, they would've been able to address it "more quickly."

"It appears that that information was stuck or siloed in that state local channel," Rowe said.

Rowe said that while it was great there was a texting chain, more needs to go "over the net," meaning, there needs to be more radio communication, which apparently there was a lack of during July 13.

Rowe lost sleep over whether attack could've been prevented

The head of the Secret Service said that if cellular capability was better on July 13, they could've launched a counter drone system sooner and potentially stopped the attack.

It is "something that has cost me a lot of sleep because of the eventual outcome of the assailant," Rowe said.

Rowe said he grappled with circumstances that could have allowed drones to spot the gunman before he opened fired.

"That what if we ... geo-located him because that counter UAS platform had been up? It is something that I have struggled with to understand," he continued. "I have no explanation for, it is something that I feel as though we could have perhaps found him. We could have maybe stopped him maybe on that particular day, he would have decided this isn't the day to do it, because law enforcement just found me flying my drone."

The countering drone system was down for about two hours and went back online at 5 p.m. ET, Rowe testified.

The gunman flew his own drone near the site hours before the shooting.

Shooter's motive still unknown, social media account discovered

The FBI deputy director said in his opening statement that the investigation remains focused on motive, identifying any potential co-conspirators and building out the timeline of the shooter's actions.

"Thus far, though absolutely nothing has been ruled out, the investigation has not identified a motive nor any co-conspirators or others with advanced knowledge," Abbate said.

Abbate also told Congress that they recently discovered a social media account from 2019 to 2020 that appeared to belong to the shooter, but Abbate couched it as preliminary.

"There were over 700 comments posted from this account," Abbate said. "Some of these comments, if ultimately attributable to the shooter, appear to reflect antisemitic and anti-immigration themes to espouse political violence and are described as extreme in nature," he said.

Rowe pressed on accountability in heated exchange

Rowe told lawmakers he is taking "immediate steps" to avoid repeating failures at the Trump rally, including expanding the use of unmanned aerial systems to check unprotected areas, improving site communications with local partners and increasing the number of security details to address a heightened security environment.

Rowe also said he heard the calls for "accountability" and noted the Secret Service is reviewing the actions and decision-making of personnel leading up to the rally.

"If this investigation reveals Secret Service employees violated agency protocols, those employees will be held accountable to our disciplinary process," he said.

Senators on both sides of the aisle said there needs to be "individual accountability" for who was responsible for what during the shooting.

A particularly heated exchange ensued between Republican Sen. Josh Hawley and Rowe over why certain individuals have not been relieved of duty, with both men raising their voices.

"Is it not prima facie that somebody has failed? The former president was shot," Hawley pressed.

Rowe responded: "Sir, this could have been our Texas School Book Depository. I have lost sleep over that for the last 17 days." Rowe was referencing the building that Lee Harvey Oswald was in during the assassination of President John F. Kennedy.

"Then just fire somebody!" Hawley exclaimed.

"I will tell you, senator, that I will not rush to judgment, that people will be held accountable, and I will do so with integrity and not rush to judgment and put people unfairly prosecuted," Rowe responded, adding that investigations are ongoing.

ABC News' Alexandra Hutzler contributed to this report.