When Arthur Edens is overtaken at his apartment door, after being stun-gunned, and object that looks somewhat like an inhaler is inserted in his mouth and something is injected. What was its purpose?
SInce the OPs question has not been answered in over 10 years, I don’t have much hope for this. But I am watching, 4th time I think, and I have a question. After the explosion, Michael runs down the hill and throws his keys and wallet into the car. That doesn’t fake his death, he had no other body to throw into the car. Is it simply that the police could release video of the burned car and let people make assumptions?
Well, what’s left of the wallet could easily be mistaken for human remains. 
Question should be asked in the Cafe Society forum, zombie or no.