The 20-year-old man who tried to assassinate former President Donald Trump first came to law enforcement's attention at Saturday's rally when spectators noticed him acting strangely outside the campaign event. The tip sparked a frantic search but officers were unable to find him before he managed to get on a roof, where he opened fire.

In the wake of the shooting that killed one spectator, investigators were hunting for any clues about what may have drove Thomas Matthew Crooks, of Bethel Park, Pennsylvania, to carry out the shocking attack. The FBI said they were investigating it as a potential act of domestic terrorism, but the absence of a clear ideological motive by the man shot dead by the Secret Service led conspiracy theories to flourish.