The FBI has not yet determined a motive in the assassination attempt against former President Donald Trump, an agency official said at a joint Senate hearing Tuesday as lawmakers pressed for answers on apparent security failures.

While the gunman’s motive remains under investigation, Paul Abbate, deputy director of the FBI, told lawmakers the investigative team is working to verify a social media account “believed to be associated” with the shooter in about 2019 and 2020.

There were more than 700 comments posted from the account, Abbate said, and some of the comments appeared to reflect “antisemitic and anti-immigration themes” and to espouse political violence.

Abbate, testifying at a joint hearing of the Senate Homeland Security and Governmental Affairs Committee and Senate Judiciary Committee, added some of the comments “are described as extreme in nature.”

Abbate also appeared to raise caution about conclusively tying the comments to the shooter at this point.

“While the investigative team is still working to verify this account to determine if it did in fact belong to the shooter, we believe it important to share and note it today,” Abbate said.

Abbate said he was offering the information “particularly given the general absence of other information to date from social media and other sources of information that reflect on the shooter’s potential motive and mindset.”

The joint hearing Tuesday is the latest response from Congress to the July 13 shooting at a Trump rally in Pennsylvania that injured the former president and left one spectator dead and another two critically injured.

The Senate Homeland Security and Governmental Affairs Committee has announced an investigation, and House leadership this week named the members of a congressional task force on the incident.

On Tuesday, Abbate also provided lawmakers with a timeline of the gunman’s actions in the lead-up to the shooting. He said the gunman visited the farm show grounds on July 7, and then practiced shooting at a sportsmans’ club the day before the assassination attempt.

On the day of the assassination attempt, the U.S. Secret Service command post was notified of a suspicious person about 25 minutes before the shooting, Abbate said.

Recently discovered video shows the gunman pulling himself onto the rooftop of the building where he ultimately committed the attack, the FBI official said.

FBI Director Christopher Wray, in an appearance before House lawmakers last week, said the 20-year-old gunman used an AR-style rifle in the assassination attempt, one that he got from his father. The director said the firearm had a collapsible stock, which could have made it more difficult to detect.

Abbate, speaking to senators on Tuesday, said they do not have definitive evidence on how the gunman got the rifle up to the roof. But based on what’s been collected, they believe he likely had the weapon in a backpack, he said.

“It’s possible that he broke the rifle down — but we don’t have conclusive evidence of that — and took it out of the bag on the roof in those moments before” and reassembled it there, he said.

“That’s one of the theories we’re looking at and working on right now,” he said.