The 20-year-old gunman who opened fire at former President Donald Trump's rally in Butler, Pennsylvania, left a chilling message online days before the incident, according to information shared with U.S. senators by top law enforcement officials.

Thomas Matthew Crooks allegedly wrote on the gaming platform Steam, "July 13 will be my premiere, watch as it unfolds," Fox News reported. This message foreshadowed the events that unfolded at the rally on that date.

Security lapse? Staged? Political hit? Opinions divided on Trump attack

While asking people about an attempted assassination of a president might raise an eyebrow, unfortunately at the 2024 Republican National Convention in Milwaukee, it's become the reality that is on… pic.twitter.com/O6WgEyk1dD

— Rebel News (@RebelNewsOnline) July 18, 2024

Investigators examining Crooks' digital footprint found images of both Trump and President Biden on his cellphone, along with searches for the Democratic National Convention dates and Trump's Pennsylvania rally schedule.

However, law enforcement sources told ABC News that the gunman's search history did not reveal a clear political motive.

The assassination attempt has raised questions about security measures at the event. Reports indicate that local police had warned the Secret Service about insufficient manpower to secure the building where Crooks positioned himself.

Former Secret Service agent and conservative commentator Dan Bongino has revealed explosive new details about the security breach that led to the near-assassination of former President Donald Trump at a Pennsylvania rally.

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Moreover, sources briefed on the investigation revealed to ABC News that Secret Service snipers spotted Crooks on a rooftop 20 minutes before he opened fire.

The shooting resulted in the death of a 50-year-old attendee and injured two others. Crooks was fatally shot by law enforcement shortly after he began firing.

As the investigation continues, authorities are scrutinizing Crooks' electronic devices and online activities in an effort to uncover his motives and any potential missed warning signs.