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In the 48 hours before he opened fire on former President Donald Trump, 20-year-old Thomas Matthew Crooks made a series of stops in and around his suburban Pittsburgh hometown.
On Friday, he went to a shooting range where he was a member, and practiced firing, a law enforcement official told CNN.
The next morning, Crooks went to a Home Depot, where he bought a five-foot ladder, and a gun store, where he purchased 50 rounds of ammunition, the official said.
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Then, Crooks drove his Hyundai Sonata about an hour north, joining thousands of people from around the region who flocked to Trump's rally in Butler, Pennsylvania.
He parked the car outside the rally, with an improvised explosive device hidden in the trunk that was wired to a transmitter he carried, the official said.
Then, investigators believe, he used his newly-bought ladder to scale a nearby building, and opened fire on the former president.
As investigators continue to search for a motive behind the attempted assassination, they are scrutinizing Crooks' movements before the attack and trying to piece together a timeline of his actions leading up to it.
Yet nearly 48 hours after the shooting, investigators are struck by the lack of leads they're finding about Crooks' mindset and possible motives.
Even after successfully breaking into his phone and searching his computer, scouring his search history and bedroom, and interviewing his family and friends, agents still haven't found evidence that would suggest political or ideological impetus for the shooting, law enforcement sources told CNN.
Instead, the evidence they have found appears to show typical online activities including an interest in computer coding and gaming, the sources said — and that has raised more questions.
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In a sign that his attack could have been even more destructive, Crooks had a remote control detonator on his body, and his car's trunk contained a metal box of explosives that was connected with wires to a receiver, the law enforcement source said.
That suggests the gunman may have been planning to set off an explosion remotely, and investigators are considering the theory that he may have been planning a distraction during the shooting.
It's unclear how Crooks assembled the explosive devices found in his car. Investigators parsing through his online search history haven't found any indication of him researching how to make home-made explosives, law enforcement officials said.
The AR-style rifle Crooks used to fire on Trump was legally purchased by his father, Matthew Crooks.
It was one of more than 20 firearms registered to the elder Crooks, which were kept at the family's home, according to Pennsylvania State Police records reviewed by investigators, the official said.
All of the guns were legally purchased.
The gunman and his father were members of Clairton Sportsmen's Club, a gun club about a 25-minute drive from his house, and enjoyed going shooting there together, according to law enforcement officials.
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Rob Bootay, a lawyer for the club, confirmed in a statement that the younger Crooks was a member.
The club, which has about 2,000 members, features a rifle shooting range that is roughly 200 yards long, according to a CNN analysis of satellite images – longer than the distance between Crooks and Trump when he fired at the former president while perched on a nearby rooftop.
The range is tucked into 180 acres of woodlands in the hills south of Pittsburgh.
"The Club fully admonishes the senseless act of violence that occurred," Bootay said, adding that he could not "make any additional commentary in relation to this matter in light of pending law enforcement investigations."
Crooks purchased the 50 rounds of ammunition on the morning of the attack at Allegheny Arms and Gun Works, a local gun store in his hometown of Bethel Park, a senior law enforcement official told CNN.
Bruce Piendl, the store's owner, said in a statement that "we are thankful that President Trump was not assassinated and our hearts and prayers go out to all victims of this horrible incident."
A spokesperson for Home Depot, where Crooks bought the ladder, said in a statement that "we condemn the violence against former President Trump, and our thoughts are with him, the other victims of Saturday's horrific events, and their families."
It's not clear whether Crooks used the ammunition or the ladder that he bought on Saturday during his attack later that day.
Matthew Crooks did not respond to requests for comment from CNN on Sunday and Monday.
On Saturday evening, before officials had publicly confirmed his son's role in the attack, he told CNN that he was trying to figure out "what the hell is going on" but would "wait until I talk to law enforcement" before speaking about his son.
FBI investigators succeeded in accessing the younger Crooks' cell phone, the agency said Monday afternoon.
While investigators had hoped that breakthough would help them understand what drove him to attempt to assassinate Trump, they're still struggling to make sense of it, law enforcement officials said.
The shooter's parents, who have been cooperating with law enforcement since the shooting, have told investigators that Crooks did not appear to have friends and did not appear to have any political leanings, a law enforcement official told CNN.
But they didn't seem to know much about what was going on in his life recently, law enforcement sources said.
CNN's Isabelle Chapman, Majlie de Puy Kamp, Curt Devine, Kyung Lah, Jamiel Lynch, Gianluca Mezzofiore and Anna-Maja Rappard contributed reporting.
