Yes.
Exactly.
And if he were Muslim it would be because of that - not because he was a homicidal whacko. Religion, like guns - is a tool to justify violence.
And...this loon was enamored with his guns.
Perhaps I am misreading your post,
but religion does not justify violence, and neither do guns. Many misguided people have attempted to do so in the past, but when you disregard the basic premises of your own religion then religion is not to blame. Does his apparently fervent belief in atheism justify his attack on those who believe in God, any God? I think not.
Yes, this guy apparently loved his guns, so what? That didn't make him a homicidal whack either. Lots of gun collectors out there, no?