No, I won't quite accept your conclusion.
I do totally accept the claim that Trump is encouraging attacks on the media, Democrats and so on. I think he's a bastard for doing so.
.
But, no, I don't accept that he or his supporters are really responsible for this. Because, as it is likely to turn out, this was a single nutcase.
There are plenty of reasons to loathe Trump. Among the reasons are that he indirectly encourages such really bad acts. And also, it seems to me, that he doesn't care about this fact.
But he's not quite culpable for this attack. Plenty of things related to it, but not the attack itself.