That's actually true, but the shooter also donated to "left-leaning" PACs, so who knows. Bear in mind that plenty of Republicans can't stand Trump either. What we do know is that he was such a terrible shot that he got rejected from his high school rifle club. The fact that he managed to kill a member of the audience is just plain bad luck.
BTW I heard about this on Substack right when it happened. Any specific question you have, there's already an entire article about it. Ask away and I will point you in the right direction.