Maruseru literally translates to Marcel in English. Marcel is a roleplayer and his characters, Maruseru and possibly Kamen, mirror his life /and/ what has been done these last three days in many ways, even the black hair dying claim.

http://steamcommunity.com/id/isuggestyouffinstead- Marcel's steam account
http://www.elitepvpers.com/forum/members/2959800-matzeloxdd.html - Elitepvpers
matzeloxdd Skype
https://www.youtube.com/user/MatzeloxDD youtube
https://soundcloud.com/matzeloxdd - soundcloud
https://plus.google.com/+MatzeloxDD - google+

Information from a mutual friend between Marcel and myself-
"According to the friend I talked to, Milkatee is either the guy who's birthday was on Monday or a friend of his.
He's not sure if it is him, but he's absolutely sure that account has something to do with him.
NiggerFaggot is someone he knew from Teamspeak." - How my contact knows these two

Milkatee, Marcel and somebody else were friends/rivals while growing up in secondary school. According to my friend, they all essentially kept trying to one-up each other, hence causing an edgy hate-love rivalry between them.
They were all outsiders.
Probably even became friends because there simply were no others to be friends with.
Milkatee used to be extremely rightist, apparently. Marcel was always mad, though.
Additionally, my friend has the feeling that it was Marcel who "accustomed" to Milkatee.
Not the other way around." -shows the outcasted life and social life that Marcel had, that likely played a part in his degeneration.

"Milkatee is in the federal army.
If it gets out that he posts like this on 4chan and has been a friend of Marcel, he'd get booted."

Audioclips-
https://instaud.io/NWs
https://instaud.io/NWI
https://instaud.io/NWD
"No more desire to have to work. It's obviously the only reason. I'd have to write my applications soon (job search) but meh.""
His motive that he gave his friend he trusted with all of this.
1. "No more desire to have to work. It's obviously the only reason. I'd have to write my applications soon (job search) but meh."
2. "Nah, I'm not able to get the situation with the noose working. I could hang myself there but I just killed the neighbor. Doesn't feel that special tbh. My Hand is bleeding and is the only thing annoying me a bit right now. Just got rid of the blood, one of my shoes is bloody but it's alright. I think I'm going to give myself up in a few days and enjoy the jail life. Maybe I'll get another neighbor over here and do the same with them. I'd have two killings on my hand then. sigh, my knife is still upstairs."
3. "I should get a girl to follow me here, I could rape her. By the way, Jadens guts feel really weird, I'm just able to pull them out of him, eww.. god." (igitt = eww)" -A translation of the audioclips

In this pastebin, Marcel Hess (selfie taken to assert this as true) offers some form of clarification on his actions.
http://pastebin.com/KWXkSuJx