Necromancy is easy. All you have to do is think really hard about the corpse right in front of you, and will it to move in the same ways in which you move yourself. Ignore their voice screaming, ignore the wailing. It's not like you can do anything about their situation, so just deal with it.
Use that corpse to fight off some next guy, one who you know also won't shut up after this. Maybe you should've known better than to go to crime alley, even if your 'boss' asked you to.
Use those two as bait, find the informant, and take them back to boss' henchmen to let them suffer the same fate as the other two. The screaming hasn't stopped, but you can handle it. If you don't do this, you're not getting paid- or maybe you will. Boss lady is weird like that, she'd probably pay either way since the cash isn't 'legit' but- it's the least you can do. And anyway, if she fires you; you're done for.
So you ignore the screaming, just enough to get the job done. The headphones block it out, but the pain in your chest is still there. You're human, or something like that, and you don't want to hurt them. That's a stupid thought, ignore it and drag yourself back. Back where? Not home, god no, just back to the shitty apartment your boss helped you rent.
The screaming hasn't stopped, but necromancy is easy, right? So you keep the headphones off and ignore the metallic taste in your mouth. Maybe waste time building something, another drone perhaps? Because you know you aren't going to sleep any time soon, not unless you want their faces flooding your dreams.
And when you finally pass out at your desk in the early hours of the morning.. you just end up waking again, tears spilling down your face as you apologise to whatever- whoever can hear you.
Apologising isn't good enough, they're gone now. You only killed one of them, and that was in self defence, so then why can you hear the others screaming? It's the same reason you can hear everyone else screaming, isn't it? They're gone and you're not. You should've been gone by now too if all you're gonna do is complain.
But honestly, there isn't any time to pity yourself. Go on, do something. Distract yourself. You're not really a loner... you have like two friends? You're not supposed to get close to anyone anymore, but whatever.
Maybe if you can make enough from the tech stuff, you won't have to deal with this anymore? You could probably get a decent lease somewhere less stabby one day, and then you wouldn't have to deal with all of this!
Well then is necromancy really the problem here? It wasn't this loud before you ran away, was it? Just messy, the same overlapping noise you heard in tour school's cafeteria. Was it really so bad back there? Did you expect to end up on your own so soon?
Poor little necromancer, stop pitying yourself. You got into this situation, get yourself out of it or stop complaining!