It’s not clear if a bullet or shrapnel hit former President Donald Trump’s ear, FBI Director Christopher Wray told the House Judiciary Committee.

"With respect to former President Trump, there's some question about whether or not it's a bullet or shrapnel that hit his ear," Wray said in response to a question from Chairman Jim Jordan asking whether the FBI has accounted for all bullets fired by the shooter. "It's conceivable, although as I sit here right now, I don't know whether that bullet, in addition to causing the grazing, could have also landed somewhere else. But I believe we've accounted for all the shots in the cartridges."

FBI agents determined Crooks' father purchased the firearm used in the shooting in 2013 and sold it to his son in October 2023, Wray said.

-ABC News’ Luke Barr and Alex Mallin

The shooter, Thomas Matthew Crooks, accessed the roof of the AGR building using mechanical equipment on the ground and piping on the side of the building, FBI Director Christopher Wray told the House Judiciary Committee.

Crooks visited a gun range a day before the shooting, Wray said.

Authorities have interviewed Crooks’ parents, who Wray describe as "cooperative."

"It's the FBI position right now that he still acted independently," he said.

Wray said he was about to have dinner with family when he heard about the shooting. He said he was "horrified and angry."

-ABC News’ Luke Barr

It appears the shooter, 20-year-old Thomas Matthew Crooks, was a "loner" and didn't have a lot of contacts in his phone, FBI Director Christopher Wray told the House Judiciary Committee.

"A lot of people describe him as a loner. That does kind of fit with what we're seeing in his devices, you know, his list of contacts, for example, is very short, compared to what you would normally see from most people. Doesn't appear to be a whole lot of interaction between him, you know, face-to-face or digital, with a lot of people," Wray said.

The FBI has conducted over 400 interviews, with "many more to conduct," he said.

-ABC News’ Luke Barr

The weapon used by the gunman had a "collapsible stock," meaning Thomas Matthew Crooks could easily conceal the gun at the rally, FBI Director Christopher Wray told the House Judiciary Committee.

"The weapon had a collapsible stock, which could explain why it might have been less easy for people to observe," he said.

Wray said that the shooter was not on the FBI's radar and there were no FBI assets at the rally.

Wray said there were 14 guns in the home where Crooks lived.

-ABC News’ Luke Barr

Authorities "have not identified an ideology associated" with the suspected shooter, Thomas Crooks, FBI Pittsburgh Special Agent in Charge Kevin Rojek told reporters on a call on Sunday.

"We're looking into his background, his day-to-day activities, any writings and social media posts that might help us identify what led to this shooting. And we have not seen anything threatening," Rojek said.

Crooks had no known mental illness history, he said.

Crooks’ family is cooperating with federal authorities, officials said.

Officials told reporters they don’t have any insights on what the suspect's actions were prior to opening fire at the shooting site, but said it's something they are investigating.

Robert Wells, the FBI's assistant director of the Counterterrorism Division, told reporters, "We are investigating this as an assassination attempt, but also looking at as a potential domestic terrorism act."

The FBI has received more than 2,000 tips, according to Rojek.

Crooks’ gun and phone will be transported to the FBI lab in Quantico, Virginia, officials said.

Rojek also confirmed there was a suspicious device that was found in the suspect’s car and said the FBI is still analyzing what it is. Another device was found in the suspect’s home, according to the FBI. Rojek described both the devices as rudimentary.

The FBI is seeing an increase of violent threats online in the aftermath of the assassination attempt, FBI Deputy Director Paul Abbate said.

"We've seen individuals go online and attempt to mimic or pose as the shooter who obviously is now deceased," Abbate said. "We're also focused on the continuing efforts, which were already substantial, given that there are national special security events on the upcoming conventions in Chicago, in Milwaukee, to work with Secret Service in the lead to play our part in protecting the people and the facilities and events there, as well."

FBI Director Christopher Wray called the assassination attempt an "attack on our democracy."

"An attempt to assassinate a presidential candidate can only be described as absolutely despicable and will not be tolerated in this country," Wray told reporters.

-ABC News’ Pierre Thomas, Aaron Katersky, Jack Date and Luke Barr