WASHINGTON (AP) — The gunman in the assassination attempt of former President Donald Trump searched online for events of both Trump and President Joe Biden, repeatedly looked up information about explosives and saw the Pennsylvania campaign rally where he opened fire last month as a "target of opportunity," a senior FBI official said Wednesday.

Investigators who have conducted nearly 1,000 interviews do not have a motive for why 20-year-old Thomas Matthew Crooks shot at Trump during a July 13 campaign rally but they believe that he conducted "extensive attack planning," including looking up campaign events involving both the current president and former president, particularly in western Pennsylvania.

The FBI analysis of his online search history reveals a "sustained, detailed effort to plan an attack on some event, meaning he looked at any number of events or targets," Kevin Rojek, the special agent in charge of the FBI's Pittsburgh field office, told reporters Wednesday.

Once a Trump rally was announced for July 13 in Butler, Pennsylvania, "He became hyper-focused on that specific event and looked at it as a target of opportunity," Rojek said. Crooks' internet searches in the days leading up to the rally included queries about the grounds where the rally was held, "Where will Trump speak from at Butler Farm Show?" "Butler Farm Show podium and "Butler Farm Show photos."

The new details add to an emerging portrait of Crooks as a man who investigators say had taken an eerie interest in explosives, major events and prominent political figures, but whose internet searches across major parties have frustrated efforts to assign a simple motive.

"We have a clear idea of mindset, but we are not ready to make any conclusive statements regarding motive at this time," Rojek said.

The FBI has confirmed that Trump was struck in the ear by a bullet during the attack. Crooks, who was positioned on the roof of a nearby building, fired eight shots before being killed by a Secret Service counter sniper.

"We have a clear idea of mindset, but we are not ready to make any conclusive statements regarding motive at this time," Rojek said.