Well, classmates aside, I think he made his preference fairly clear, when he tried to blow Trump's head off. I mean, there is THAT.
It doesn't seem that we have a very clear picture of where his head was at, in the two years since HS and when he climbed up on that roof. We know that the extreme left/Democrats have historically been more prone to start shooting political opponents.
You have to admit, that a staunch right wing conservative or libertarian would be acting against their own interests by killing Trump. (Unless you think the sole motivation was to martyr him, which seems superfluous, since Trump was already the favorite to be elected)