Fountain of Knowledge

Alright, so my main character--let's call him Alan--is a private investigator on the trail of a serial killer. Said serial killer--for now, named Bob--has kidnapped and murdered a half-dozen teenagers over the past three years, murdered Alan's love interest, kidnapped another young girl whom Alan is fond of, and rendered Alan's friend Cathy unconscious. Basically this Bob has done everything he can to set Alan on edge.

What happens is that Alan is in Bob's house, trying to wake Cathy up, when he gets shot at by Bob. Bullet misses and Bob flees out the door. Alan chases after him and shoots him twice in the back. Bob hits the ground and begs for his life. Alan ignores him and puts a bullet through his head, killing Bob. Alan then notices he himself been shot (either Bob's earlier shot didn't miss, and he just didn't realize it, or he shot Alan right before Alan put an end to him). Alan goes under and is eventually brought to hospital, where he recovers due to Bob's remarkably poor firearm skills. {e:sarcasm}

Just to be clear, Bob is unequivocally the culprit behind all of the crimes listed above--this isn't a case of mistaken identity or misleading facts. The police are going to know for sure afterwards that he's the killer, because there's incriminating evidence stashed in his house.

My question is, what is going to happen to Alan? What are the specific things that he's going to be charged with and, if he gets sent to jail, how much time is he looking at doing? And finally: is there any chance that he will be acquitted of any/all of these charges?

Please and thank you

Summer~