WASHINGTON (AP) — Former President Donald Trump has agreed to be interviewed by the FBI as part of an investigation into his attempted assassination in Pennsylvania earlier this month, a special agent said on Monday in disclosing how the gunman prior to the shooting had researched mass attacks and explosive devices.

The expected interview with the 2024 Republican presidential nominee is part of the FBI’s standard protocol to speak with victims during the course of its criminal investigations. The FBI said on Friday that Trump was struck by a bullet or a fragment of one during the July 13 assassination attempt at a campaign rally in Butler, Pennsylvania.

“We want to get his perspective on what he observed,” said Kevin Rojek, the special agent in charge of the FBI’s Pittsburgh field office. “It is a standard victim interview like we would do for any other victim of crime, under any other circumstances.”

Through roughly 450 interviews, the FBI has fleshed out a portrait of the gunman, Thomas Matthew Crooks, that reveals him to be a “highly intelligent” but reclusive 20-year-old whose primary social circle was his family and who maintained few friends and acquaintances throughout his life, Rojek said.

His parents have been “extremely cooperative,” with the investigation, Rojek said. They have said they had no advance knowledge of the shooting, a statement the FBI considers credible since Crooks had not been doing anything public in the weeks prior to the attack that would have aroused their suspicions.

The FBI has not uncovered a motive as to why he chose to target Trump, but investigators believe the shooting was the result of extensive planning, including the purchase in recent months of chemical precursors that investigators believe were used to create the explosive devices found in his car and his home and the use of a drone about 200 yards from the rally site in the hours before the event.

In addition, Rojek said, Crooks looked online for information about mass shootings, improvised explosive devices, power plants and the attempted assassination in May of Slovakia’s populist Prime Minister Robert Fico.

FBI Director Christopher Wray told Congress last week that on July 6, the day Crooks registered to attend the Trump rally, he googled: “How far away was Oswald from Kennedy?” That’s a reference to Lee Harvey Oswald, the shooter who killed President John F. Kennedy from a sniper’s perch in Dallas on Nov. 22, 1963.

New details, meanwhile, were emerging about law enforcement security lapses that preceded the shooting, with Sen. Chuck Grassley, the top Republican on the Senate Judiciary Committee, releasing text messages from members of the Beaver County Emergency Services Unit that showed how local officers had spotted a suspicious-looking man who turned out to be Crooks lurking around in the hour before the shooting.

“Kid learning around building we are in. AGR I believe it is,” one officer wrote to other counter-snipers, including a photograph of Crooks. “I did see him with a range finder looking towards stage. FYI. If you wanna notify SS snipers to look out. I lost sight of him.”

AGR is a reference to a complex of buildings that form AGR International Inc. Crooks scaled the roof of one of the buildings of the compound and fired eight shots at the rally stage with an AR-style rifle. Trump said he was “shot with a bullet that pierced the upper part of my right ear,” and he appeared in the days later with a bandage on the ear. One rallygoer, Corey Comperatore, was killed, and two others were injured. Crooks was shot dead by a Secret Service counter-sniper.

In an interview with ABC News, a Beaver County officer who sounded the alarm said that after sending the text, “I assumed that there would be somebody coming out to speak with this individual or find out what’s going on.”

Another officer told ABC News that the group was supposed to get a face-to-face briefing with the Secret Service counter-snipers but that never happened. An email to the Secret Service was not immediately returned Monday.