Interesting that you mention that "he's an angry man", ALP.
I did a quick google, just in case this was one of those pics where what is happening is not what the caption says.
And the caption in this case is correct.
But there was some back story. The acid guy's motel was up against the wall. He'd been firebombed by the KKK already and he was - apparently - pushed into doing something to fight desegregation. He was also described as a civic minded guy, involved in local charities and community groups. So he prolly was an angry man. Who can say how much anger was directed at his situation, and how much at the people in the pool?
None of which should be taken as any sort of justification for abhorrent behaviour, but we're right back at the free will discussion!