Zimmerman was a vigilante and not a Neighborhood Watchman.

[Kaleva]

4. Most murderers don't give personal info to police dispatch...

before committing a crime and most don't stand around waiting for the police to show up after the crime has been committed.

I think he could be charged with involuntary manslaughter.

"Involuntary Manslaughter"

"The death of (victim) was caused by the culpable negligence of (defendant). "

"The negligent act or omission must have been committed with an utter disregard for the safety of others. Culpable negligence is consciously doing an act or following a course of conduct that the defendant must have known, or reasonably should have known, was likely to cause death or great bodily injury."

http://www.arnoldlawfirmllc.com/CM/Custom/Manslaughter.asp

Zimmerman knew from his training not to confront suspicious people and he was told by police dispatch that there was no need to follow Trayvon but he did anyways.