Updated

Trump rally shooter Thomas Matthew Crooks was perceived by the U.S. Secret Service as a "person of interest," not yet a "threat" after law enforcement saw him acting suspiciously and determined he had a golf range finder, according to Secret Service Spokesman Anthony Guglielmi.   

Crooks was only identified as a threat when he "retrieved the weapon" and climbed onto the roof of a building just prior to the shooting on Saturday in Butler, Pennsylvania, according to Guglielmi, who added that a threat requires, "a different protocol and a different course of action than a person of interest." 

Guglielmi maintains that it was only once Crooks retrieved his weapon and got onto a building's roof in the area where Trump was holding the rally that he was identified as a threat. 

Soon after that, Butler Township police officers confronted Crooks on the roof and he pointed his weapon at one of them, who then dropped off the roof. 

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Donald Trump is seen with blood on his face surrounded by secret service

Former President Trump is seen raising his fist after being shot on Saturday, July 13, in Butler, Pennsylvania. (Rebecca Droke/AFP via Getty Images)

Crooks then fired on former president Trump and was taken out by a Secret Service counter sniper. 

The FBI is leading the investigation into the attack on Saturday at the Trump campaign event. The motive as to why Crooks opened fire at Trump remains unknown.

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Trump rally sloped roof

The building where the Trump rally shooter was positioned, left, and snipers set up on a sloped roof behind former President Trump's podium at the event. ( Fox News Digital/Glen Van Tryfle/TMX/Reuters)

Secret Service and FBI officials told U.S. senators during an all-members briefing on Wednesday that Crooks, 20, wrote a threatening message on the gaming platform "Steam" days before the attempted assassination.

Crooks headshot next to a cell phone.

Trump shooter Thomas Crooks' transmitter and cellphone, obtained by WPXI. (WPXI/ AFP handout/ AP's Gene J. Puskar)

According to the officials, Crooks allegedly wrote: "July 13 will be my premiere, watch as it unfolds."

Donald Trump is seen with blood on his face

Trump is seen being rushed off the stage following the shooting in Butler, Pennsylvania. (Rebecca Droke/AFP via Getty Images)

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In the wake of the incident, Secret Service Director Kimberly Cheatle is facing pressure to resign, with House Speaker Mike Johnson, R-La., telling FOX Business on Thursday that he is ready to call on President Biden to fire her.

Fox News' Lawrence Richard and Jacqui Heinrich contributed to this report.