So... It is mostly just gratuitous violence. That kind of disarms any possible impact: we already know how every short ends (with the notable exception of Missy's story).
The ones I liked the most were the ones in which the violent display actually had a reason beyond mere psycopathy, like Missy's story (my favourite and most deeply felt, by far... Really tragic), the one about the cheating girl giving the guy STDs and the other one about the cheating jealous guy, near the end. Even though the one about the kid snapping and killing everyone at school and the hitman made sense, they just didn't feel the same. Didn't the kid's life improve a little after the bully disappeared? I did like how you tied the boy's story to the teacher's one, though. It was subtle enough.
The psycho killers getting their way with killing without consequences felt way too improbable.
And finally, I see potential here. But maybe you should've explored the rest of the signs of decadence: the cheating partners, the ennui, the anger, the pollution and destruction of the Earth, poverty and extreme wealth living next to each other... You have more topics than just killing. Even violence has greater variety than just this.
I like your minimalistic style and the music went well with each short.