I, on a personal level, am skeptical about the usage--or at least the possible over-usage--of mood-altering medications primarily because we know so little about the way they work. See TFA as an example. I'm doubly skeptical on using SSRIs and other drugs on childrens, adolescents, and even young adults, as there are even more uncertainties about these drugs on still-developing brains!
Having said that, SSRIs are common medications today. The kind of people who are suicidal or have such a mood-disorder that going on a shooting rampage seems like a good idea are exactly the people for whom you would expect SSRIs to be prescribed! In other words, are SSRIs causing these issues (and earning your blame), or were the problems there to begin with?
I don't know, and I don't know of any studies or other medical evidence that points either way. IMH(and not not scientifically grounded)O, I would, like you, suspect some causal relationship.