The gunman who tried to kill former President Donald J. Trump searched online for details of John F. Kennedy’s assassination a week before the shooting, apparently typing, “How far away was Oswald from Kennedy?” the director of the F.B.I. told lawmakers on Wednesday.

The disclosure by the F.B.I. director, Christopher A. Wray, to the House Judiciary Committee, appeared to be a possible first indication that the shooter began to contemplate an assassination. That same day, July 6, he appears to have registered to attend the rally in Butler, Pa., where Mr. Trump was set to speak, Mr. Wray added.

“That’s a search that obviously is significant in terms of his state of mind,” Mr. Wray said, noting that the gunman’s interest in public figures around that time “became very focused on former President Trump and this rally.”

Even as Mr. Wray cautioned that the investigation was still continuing, he disclosed several new details about the shooting during a hearing that stretched over four hours.

Mr. Wray spoke more specifically about the injury to Mr. Trump’s ear, although he was unclear about what caused it. He at first said “there’s some question about whether or not it’s a bullet or shrapnel that hit his ear.”

But Mr. Wray then appeared to suggest that it was in fact a bullet when he added, “I don’t know whether that bullet, in addition to causing the grazing, could have also landed somewhere else.”

The gunman visited the site of the rally the next day, July 7, one of three visits Mr. Wray detailed. In the first, he spent about 20 minutes at the scene. He returned twice on the day of the shooting, July 13, for about 70 minutes in the morning, and then later that afternoon, when he appeared to fly a drone in the vicinity for about 11 minutes.

“It appears that around 3:50 p.m., 4:00, in that window, on the day of the shooting, that the shooter was flying the drone around the area,” Mr. Wray said, noting that it was “not over the stage, but about 200 yards, give or take, away from that.”

The shooting left Mr. Trump’s ear bloodied, killed a rallygoer who had been sitting in the stands and seriously injured two others.

Secret Service snipers killed the gunman, Thomas Crooks, 20, after locating him on a nearby roof. Mr. Crooks was armed with an AR-15-style rifle and had magazines for the rifle and a bulletproof vest in his car along with the drone. The F.B.I. managed to reconstruct the flight path of the drone, though it did not recover any video or pictures from it.

The gunman’s father had purchased the gun more than a decade ago, but Mr. Wray said on Wednesday that the son bought the rifle from his father and that the family had 14 firearms in the house. Mr. Wray described the younger Mr. Crooks as “a fairly avid shooting hobbyist.”

“We believe based on what we’ve seen that his father, after purchasing the gun, legally sold the gun to his son,” Mr. Wray told lawmakers, saying he did not have the amount of the transfer. The father purchased the weapon in 2013 and sold it to his son in October 2023, he later added.

The day of the shooting, at about 1:30 p.m., Mr. Crooks bought 50 rounds of ammunition, Mr. Wray said.

The rifle had a collapsible stock, Mr. Wray added, suggesting that perhaps that made the gunman less noticeable, and he confirmed that eight bullet cartridges were recovered from the roof where the gunman opened fire.

So far, Mr. Wray said, the F.B.I. has not found a motive for the shooting, though the gunman appears to be a loner with a small number of contacts in his phone. Still, the bureau continues to examine the gunman’s electronic devices for additional clues about Mr. Crooks’s mind-set and movements beforehand.

“It’s fair to say we do not yet have a clear picture of his motive,” Mr. Wray said, adding that the bureau’s behavioral analysis unit was assembling a profile of the shooter.

He noted that the gunman used encrypted messaging applications and described explosive devices found in the gunman’s car as “crude” but said they were able to be detonated remotely.

Agents had recovered a ladder that Mr. Crooks had bought the morning of the shooting, Mr. Wray said, adding that it was not at the scene of the shooting. Investigators found a bloody Home Depot receipt for the ladder in the pocket of Mr. Crooks. Mr. Wray said that Mr. Crooks did not use the ladder but instead climbed on some equipment and piping on the side of the building to reach the top of the building.

While the F.B.I. typically does not discuss open investigations, the extraordinary circumstances and deep interest in the failed assassination attempt allow the bureau to inform the public. The F.B.I. has conducted more than 400 interviews, and scores of bureau personnel are involved in the investigation.

“The attempted assassination of the former president was an attack on our democracy,” Mr. Wray said, adding, “I recognize the congressional and public interest in this case.”

Indeed, Mr. Wray seemed eager to provide new information at the outset but sat through dueling opening statements rife with partisan pronouncements. Only about 30 minutes into the hearing did he have an opening to disclose more details about the drone found in the gunman’s car.

Lawmakers have called a series of hearings this week to examine the shooting and the broader security failures to understand how a would-be assassin was able to take aim at Mr. Trump.

Among the lingering questions are why the Secret Service’s security perimeter did not include the building from which the gunman eventually fired and why no law enforcement officer was stationed there during the rally. Officials have also asked why Mr. Trump was allowed to take the stage when law enforcement, including the Secret Service and the local police, was searching for a suspicious person.

During testimony before Congress on Monday, Kimberly A. Cheatle, then the head of the Secret Service, faced withering questions from both sides of the political aisle and repeatedly declined to answer questions about the security lapses that led to the assassination attempt.

Facing mounting calls to step down, Ms. Cheatle resigned a day later.

On Tuesday, Col. Christopher L. Paris, the top Pennsylvania police official, told lawmakers that two snipers from a Butler County tactical unit had first noticed Mr. Crooks acting suspiciously about 15 minutes before Mr. Trump began speaking.

That unit had been responsible for monitoring the roof of a nearby warehouse, where Mr. Crooks ultimately began firing his gun, Colonel Paris testified. He said that the two snipers, who were stationed by the second-story windows of an adjacent building, left their post to go look for Mr. Crooks shortly before the shooting began.

On Wednesday, the Butler County district attorney, Richard Goldinger, who oversees that tactical team, released a statement saying that some of this had been “misstated.” One of the snipers had left the building to track down Mr. Crooks, Mr. Goldinger wrote, but returned before the shooting began, while the other stayed inside the whole time. He added that neither of them could see Mr. Crooks on the roof from where they were stationed.

Mr. Goldinger’s statement did not address whether the local tactical team had been given responsibility for securing that rooftop, though he had explicitly denied that in the days immediately after the shooting.

Even as the F.B.I. has not faced the same criticism as the Secret Service, Mr. Wray was drawn into the political fray on Wednesday when asked about Project 2025, a set of conservative policy proposals for a future Republican administration that has angered Democrats.

Pressed about what the initiative would mean for the F.B.I., Mr. Wray emphasized that the bureau needed to retain its independence. Answering directly to the president, he said, would not be a “wise reporting structure.”

Asked about an Iranian plot to kill Mr. Trump, which was not included in the Secret Service’s threat assessment for the rally in Butler, Mr. Wray declined to discuss specific details about such national security threats.

“We need to recognize the brazenness of the Iranian regime,” he said, adding that there was a process for sharing such information to the Secret Service in a timely way.