(NewsNation) — The weapon used by the gunman who shot at former President Donald Trump during a campaign rally had a “collapsible stock” which may have made it hard to identify, FBI Director Christopher Wray told lawmakers Wednesday.

Wray revealed the new details during a House Judiciary Committee hearing about FBI oversight, where lawmakers questioned him about the July 13 shooting in Butler, Pennsylvania, that killed one attendee and wounded two others.

Other information Wray talked about included the fact that the shooter, identified as Thomas Matthew Crooks, 20, appeared to have used a drone at the event site hours before the assassination attempt.

NewsNation will present a special report on the assassination attempt against former President Donald Trump on Thursday at 10 p.m. ET. Senior National Correspondent Brian Entin will anchor from Butler, Pennsylvania, near the site of the rally, as NewsNation relives the moment of crisis and the major unanswered questions about what went wrong. Here’s how you can watch.

Wray said the FBI’s preliminary investigation found the drone was flown about 200 yards away from the stage at around 3:50-4 p.m., though he stressed the probe into the shooting is still ongoing.

FBI agents also found three explosive devices in the aftermath of the attack: two in Crooks’ vehicle and one in his residence.

“I would say these are relatively crude devices themselves, but they did have the ability to be detonated remotely,” Wray told the House Judiciary Committee. In addition, there were eight cartridges retrieved by FBI agents on the rooftop of the building where the shooter had been. To get on the roof, Wray said, Crooks likely used mechanical equipment on the ground and vertical piping — not a ladder.

On Crooks’ laptop, Wray said, agents found a Google search for “How far away was Oswald from Kennedy?” which is a reference to Lee Harvey Oswald, the man who killed President John F. Kennedy in 1963.

“That is a search that is significant in terms of his state of mind,” Wray said. Crooks looked it up, Wray testified, on the same day he appears to have registered for the Trump rally. Before the shooting, Crooks had been particularly consumed by Trump, though he also had photos on his phone of Democratic President Joe Biden and others.

An exact motive for the shooting has not been determined yet, according to Wray.

Crooks was ultimately killed by the Secret Service just moments after he began firing at Trump and the crowd.

Trump assassination attempt fallout

The law enforcement response to the shooting has been heavily criticized.

Congressional sources confirmed to NewsNation that Crooks had been identified as a possible threat over an hour before he committed the act. Twenty minutes prior to the attack, he was spotted by law enforcement looking through a range finder, sources said.

Following the rally, Secret Service Director Kimberly Cheatle faced bipartisan pressure to resign, which she did Tuesday. Cheatle had previously spoken at a congressional hearing where she said the Secret Service “failed” on the day of the shooting.

Wray, in his opening statement Wednesday, offered his condolences to the victims of what he said was a “horrific” assassination attempt, including “the friends and family of Corey Comperatore, who by all accounts lost his life protecting others from danger,” the two people who were injured “and, of course, to former President Trump and his family.”

“As I’ve said from the beginning, the attempted assassination on the former president was an attack on our democracy and our democratic process, and we will not and do not tolerate political violence of any account, especially a despicable account of this magnitude,” Wray said. 

Reporting by NewsNation correspondent Evan Lambert and The Associated Press contributed to this report.