Dude, you're most likely deep down feeling guilty that your friend killed himself... thinking things like 'I should have done something.' First of all, that's not true, there's nothing you could've done... anyway yah you're prolly deep down feeling guilty, and for whatever reason killing the character hooked you, because in a direct way you WERE responsible for killing the game character (not your friend tho)and you displaced your grief and guilt over your friend's death onto a game character, so it just seeped out. Basically the game was like a drill digging into hidden feelings and letting them out. I think that seeing that the character's name was the same as your friend's is secondary. I think even if you hadn't noticed that, the feelings would still've been there, and the only thing seeing the name did was...kind of like to reinforce and confirm the guilt feelings.
I'm a bit high, so I really hope that made sense, and i'm REALLY sorry about your friend. My cousin shot himself when we were 16 and it sucks.