Federal investigators now have two working theories as to how would-be Trump assassin Thomas Matthew Crooks was able to get an AR-15 DPMS AR-15 rifle onto the roof of a building with a clear line of sight on the former president’s podium in Butler, Pennsylvania last Saturday.

According to a report from Fox News, one source who had been briefed on the investigation stated that it is believed Crooks hid the rifle behind an air-conditioning unit he used to climb on top of the AGR International Building. Another theory contends that the rifle — which was purchased by the gunman’s father — was hidden in the gunman’s backpack.

The source told the outlet that hiding the rifle in his backpack would require a significant amount of time for disassembling and reassembling the firearm. It is therefore believed that the 20-year-old likely hid the weapon behind the AC unit.

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The latest report comes as questions continue to swirl surrounding the events leading up to the shooting and security failures surrounding the event.

Secret Service personnel first took notice of Crooks, who was wearing the backpack, as he surveyed the rally grounds roughly an hour before the shooting. He was seen using a golf range finder to scope out the former president’s podium.

Investigators have stated that Crooks was initially viewed as a “person of interest” when he was seen lurking around the grounds before the rally began.

Once he climbed onto the roof, Crooks he was identified as an “elevated threat.” He was confronted by a local police officer who was holding onto the roof with two hands after being hoisted up by his colleagues. Once he pulled himself up and peered over the roof, Crooks aimed his rifle at the officers, prompting the officer to drop roughly eight feet down.

The local officers then announced over a radio channel that they had encountered an armed suspect on the roof.

Investigators are also probing whether Crooks used a drone to survey the rally grounds prior to the attempt on the former president’s life, which killed retired firefighter Corey Comperatore as he shielded his family from gunfire. Two additional victims — David Dutch, 57, of New Kensington, PA and James Copenhaver, 74, of Moon Township, Pennsylvania — were critically injured.

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