F.B.I. officials told members of Congress on Wednesday that the gunman who tried to kill former President Donald J. Trump used his cellphone and other devices to search images of Mr. Trump and President Biden, along with an array of public figures.

The 20-year-old gunman, Thomas Matthew Crooks of Bethel Park, Pa., also looked up dates of Mr. Trump’s appearances and the Democratic National Convention, according to people on two conference calls held to answer lawmakers’ questions.

At least once, his browsing history signaled concerns about his own mental state.

The disclosures, made during private briefings to lawmakers by the F.B.I. and the head of the embattled Secret Service, offered the most complete portrait so far of a would-be assassin with no criminal history, or even clearly discernible political beliefs, who came close to killing Mr. Trump. Still, no clear motive for the attack has emerged.

The official assessment aligned with recollections of people who knew him. Several former classmates have said they never heard the gunman express any particular political ideology. But Vincent Taormina, a former classmate who said he attended middle school and high school with the gunman, said in an interview that Mr. Crooks showed a general disdain for politicians in both parties.

He recalled one instance when the two were in seventh grade. During a classroom political debate, Mr. Taormina voiced his support for Mr. Trump. Mr. Crooks seemed incredulous.

“He says, ‘Aren’t you Hispanic? And you like Trump?’” Mr. Taormina said. “He said, ‘That’s a little stupid.’”