The would-be assassin
By 
The federal authorities have revealed his identity:
Law enforcement authorities have identified the man who made an assassination attempt on former President Donald Trump at a rally in Pennsylvania on Saturday.
The FBI said the shooter, who is dead, was identified as 20-year-old Thomas Matthew Crooks of Bethel Park, Pennsylvania. A motive was not clear.
The gunman was immediately “neutralized” by the Secret Service, chief of communications Anthony Guglielmi said.
Bethel Park is a predominantly white, relatively well-to-do city in the southern reaches of greater Pittsburgh. The site of the rally, Butler, is about an hour’s drive north of Pittsburgh.
Pennsylvania voter records listed a Thomas Matthew Crooks with the same address and birth date as a registered Republican, though it was not clear from the records when that was put in place.
We have no idea what the shooter’s motives were, and his being a registered Republican is not dispositive of any theory. But given that the last assassination attempt against an American president was by a guy literally trying to impress a character Jodie Foster played in a movie, to assume that the motivation was someone who opposed Trump’s politics from some kind of left position would be extremely stupid.