Who massacres worshippers?

What kind of cause can convince a person that pulling the trigger on a weapon outside of a place of peace and reverence, that placing your sights on innocent people without weapons or defenses, is a course of action you should take?

What being or individual would be impressed by that, and why would you want to impress that individual and not shove the barrel of your weapon into that person’s mouth and pull the trigger?

Is it fear? What could you be so afraid of that you would murder hundreds of innocents?

What I got from the latest Supernatural episode :

Castiel : Dean I’m going to fuck things up.

Dean : No Cas’. I’m coming with you.

Castiel : Oh my dad Dean. I’m an adult you know. I’ll be okay.

Castiel : *looks at camera* I lied.

I was fine and then I started imagining the last scene in the series as a scene where Bellamy and Clarke are on a hill staring off at the sunset watching their kids and their friends play a game of tag down below, wrapped in each others arms and him asking ‘what now, princess?’ and her answering 'whatever the hell we want’ as she snuggles into his side and he kisses her forehead and it pans off and they’re both smiling and hapPY AND NOW I AM NOT FINE. I’M NOT FINE AT ALL DAMN IT