Trump's attempted assassin posted message before shooting: 'July 13 will be my premiere, watch as it unfolds'

Thomas Matthew Crooks apparently teased an attack online days before he climbed onto a roof and opened fire at a Pennsylvania campaign rally, killing one and injuring others, including former President Donald Trump, Fox News has learned.

Secret Service and FBI officials told U.S. senators during an all-members briefing on Wednesday, July 17, that Crooks, 20, wrote a threatening message on the gaming platform "Steam" days before the attempted assassination in Butler, Pennsylvania, on July 13, Fox News’ Jacqui Heinrich reported.

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