While I'm not sure about laws regarding this stuff in the Far East (in this case China), in the West, he wouldn't be guilty of any crime, since it was an accident occurring while defending himself. I think it wouldn't even be self-defence legally speaking, since all he did was push the guy away in what appeared to be an otherwise safe situation. Actually, the victim kind of killed himself, by removing the pen, which caused him to bleed way more. Yet again, I have little to no idea about the laws regarding this stuff in China.
His next set of actions, going by the assumption that he's guilty of involuntary manslaughter are down right stupid since they are further crimes and he goes about them stupidly (IP addresses, anyone?). He's basically setting himself up for terrible penalties. Logically speaking, if you're too afraid to call the police and look something up, the first thing to look into are the relevant laws (that won't hurt you, either way), then figure out the next course of action. (Which should be to call the police — well actually that should have been his first course of action to begin with, but that is an incredibly disconcerting situation to wake up to, to say the least — but we're talking about fiction-land, so rules apply as the author wills it.)
Also, does it not occur to him that apartment walls are thin? Even before doing anything else, there's already plenty of incriminating evidence that he has no way of handling before he starts acting against his own interests. (Considering the nature of the work and protagonist, morals can be put to the side on this one.)
There were so many problems, I couldn't get any further than his decision to dispose of the body.