Former President Trump's would-be assassin would have been at work on Saturday, but told his boss that he needed the day off because he had "something to do," according to reports.

Thomas Matthew Crooks was shot dead by Secret Service agents after firing five rounds, grazing Trump's ear, killing firefighter Corey Comperatore and injuring two others at a rally in Butler, Pennsylvania.

But law enforcement sources told CNN that the 20-year-old told his boss that he would be back at work on Sunday. 

Crooks listed himself as unemployed in 2020, but he worked most recently as a dietary aide at Bethel Park Skilled Nursing and Rehabilitation Center, a state-licensed transitional facility.

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An undated image of Thomas Matthew Crooks.

An undated image of Thomas Matthew Crooks (Handout via AFP)

The center's administrator, Marcie Grimm, said in a Sunday statement that Crooks "performed his job without concern" and his background check was clean.

Nursing home where Trump rally shooter worked

Nursing home where Trump shooter Thomas Matthew Crooks worked. (Michael Ruiz/Fox News Digital)

Crooks' "newer model" phone and a gray 12-button remote transmitter were recovered from beside his body after he was shot, according to photos obtained by WPXI.

The transmitter is believed to have been connected to an explosive device in Crooks' car – investigators suggested in an interview with the New York Post that he may have planned to stage a distraction during the shooting. 

Thomas Matthew Crooks crawling on a roof moments before he attempted to assassinate former President Donald Trump.

Blurry cellphone video shows a rallygoer's perspective of Thomas Matthew Crooks crawling on a roof moments before he attempted to assassinate former President Donald Trump. (DJ Laughery)

Although they have gained access to his phone and laptop, investigators have yet to determine a possible motive for Crooks' assassination attempt. But they are beginning to piece together a clearer picture of his actions leading up to the shooting that day.

Roughly three hours before the shooting, Crooks aroused suspicion when he passed through magnetometers at the rally's security screening area with a range-finder, which looks like a small pair of binoculars and is used by target shooters and hunters to measure distances when setting up a long-range shot. 

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Undated file photo of Thomas Matthew Crooks

Thomas Matthew Crooks was the shooter in the assassination attempt on former President Donald Trump in Butler, Pennsylvania, on Saturday, July 13, 2024. (Fox News Digital law enforcement source)

A law enforcement source told Fox News Digital that a local officer saw a suspicious man carrying a range-finder "in or just-outside" the venue before Trump took the stage.

That sighting was shared with state police, according to the source, and there was a discussion about whether the man was carrying a pair of binoculars to try to see the rally better.

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A home believed to be connected to the shooter in the assassination attempt of Republican presidential candidate former President Donald Trump

News crews line the yard of a house across the street from the home believed to be connected to the shooter in the assassination attempt of former President Trump, Monday, July 15, 2024, in Bethel Park, Pennsylvania. (AP Photo/Gene J. Puskar)

Crooks was able to gain access to the building's roof by climbing on top of an air conditioning unit, ABC News reported.

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Fox News Digital's Michael Ruiz and Sarah Rumpf-Whitten contributed to this report.