Ahaha, so my thoughts about the meaning of "Timcampy cover" back then were true.
Now as for who is killer. Only two possibilites:
Allen
"Link"(the one of Crows)
Thats pretty much the only two things capable of it. I am more on that it was one of Crows, since Crows were hyped as "powerful" things.
EDIT: NOw Obviously its not suicide - had he shot himself, he would have fallen on the ground, not sitting in there, instead he was shot from close range away, hence the blood being higher than cross is cross was pushed away by shot, with bullet mostly going through, splattering the blood behind him, then he "slid" down into that position (the trail of blood shows this) at the same time dropping his own gun