Determinism is a helluva drug...
But seriously, we gotta look at the structural issues at play in things like this. A lot of gun control advocates want to point at things like this, and say, see, this shit doesn't happen in any other country in the world, obviously the guns are the problem, we need to take the guns! But when you look at other countries, you see that the US is one of the few that has both guns and almost no social safety nets. The proposed solution on the left is never "fix the problems that lead to crime and violence"; rather, it's "take the tools used to commit crime and violence"
You can use the facile response of saying, no, this is all on Cruz, he made a choice. And it's true, kind of, except that his choices were significantly constrained by the social conditions that were imposed on him. That's not saying that what he did was right, nor does it make it the 'fault' of the people he victimized. But things like this simply do not happen in a vacuum.
Here's another way of looking at it.
If you take a dog as a puppy, starve it, leave it outside all the time, ignore it, kick it, never give it any positive interaction, and always punish it for any 'infraction' when you've never put in any time to teach it better, are you going to be surprised when it mauls someone? Why do you expect any other animal to behave better than a dog just because it walks upright and has no fur?