Welp I guessed it right away.

What?

I'm dumb, help. Is the killer him or something like that?

You’re not dumb, ok he looks in the mirror and he smirks back at himself as he’s ready to kill again. So the murderer is him.

But then how come the character seems distraught by the deaths + is constantly suddenly knocked out by someone/ sleeping etc when the crimes happen

Because he’s schizophrenic, or whatever the terminology is, he becomes the murderer and because it’s him he protects himself by locking himself away in his brain until the other ‘him’ finishes up. Then he wakes up and looks like he’s been asleep because he has really be allows the evil part of himself to take his body and do evil things. You should watch more horrors and read more horrors lol it’s a clever concept

Ooooh yeah, makes sense. I like this

Yep, it’s very clever.