FBI agents on Monday entered the Bethel Park, Pennsylvania, home of would-be Trump assassin Thomas Crooks.

Federal authorities say Crooks, 20, shot at Trump with an AR-15 while the former president was speaking at his rally in Butler on Saturday evening, but the gunman missed his intended target and hit three other victims — one of whom died.

"The FBI continues to investigate the shooting incident at the July 13 rally in Butler, Pennsylvania, as an assassination attempt on former President Donald Trump and as potential domestic terrorism.," the FBI told Fox News' David Spunt in a statement. "The investigation is still in the early stages and the FBI is providing the following updates: FBI technical specialists successfully gained access to Thomas Matthew Crooks’ phone, and they continue to analyze his electronic devices. The search of the subject's residence and vehicle are complete."

The FBI added that it has "conducted nearly 100 interviews of law enforcement personnel, event attendees, and other witnesses," and the agency's "work continues."

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Reuters photos show two FBI agents in blue shirts entering and exiting Crooks' home on Monday morning.

Roads leading up to the shooting subject's home have been taped off since late Friday after the shooting.

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"We have a 24/7 command post in Pittsburgh as well as here at FBI headquarters and we are dedicating every resource that we have at our disposal," said Robert Wells, the assistant director of the Counterterrorism Division at the FBI. "Our number one goal here is to identify the motive of the subject and determine whether he had any other associates or anyone else that was involved at this point."

The FBI is investigating Crooks' actions as an assassination attempt.

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The 20-year-old allegedly shot at rally-goers from the rooftop of a building some 160 yards away from where Trump was standing on Saturday.

The gunman ended up killing 50-year-old Corey Comperatore, a former fire chief of Buffalo Township, and injuring two others that Pennsylvania State Police identified as David Dutch, 57, and James Copenhaver, 74. Secret Service agents then returned fire, killing Crooks while he was on the rooftop.

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Crooks held a membership at the Clairton Sportsmen's Club in nearby Clairton for at least a year, according to a statement sent to Fox News from the gun club's attorney, Rob Bootay.

"Beyond that, the Club is unable to make any additional commentary in relation to this matter in light of pending law enforcement investigations. Obviously, the Club fully admonishes the senseless act of violence that occurred yesterday. The Club also offers its sincerest condolences to the Comperatore family and extends prayers to all of those injured including the former President," Bootay said.

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Crooks graduated from Bethel Park High School in 2022 and was one of about two-dozen students to receive a $500 "star award" from the National Math and Science Initiative. The 20-year-old was a registered Republican but donated $15 to a Democratic, Chicago-based PAC in 2021.

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Federal authorities are asking anyone with information about the incident to send tips to FBI.gov/butler or call 1-800-CALL-FBI.

Fox News' Sarah Rumpf-Whitten and Scott McDonald contributed to this report.