This sucks all around. You can blame the family for not agressively pushing him into decent treatment, you can blame the numerous previous victims for not pressing charges, you can blame the cops for not putting the pattern together before it was too late, you can blame who ever it was who allegedly fucked this guy up in his childhood. None of that blame brings back the two dead people.
At least he turned the gun on himself. That sucks too, but he was the only one who had the guts to stop himself from doing it again.
A disaster like this is usually because of multiple failures.