Argh, it's so frustrating to see people argue about how tall they were and how much they weighed. We'll see the facts come out, right now we're relying on what Zimmerman said, and what Martin's parents have said, and what an unidentified eye witness has said. We have not heard anything about forensic evidence and we know nothing about Zimmerman's injuries except for what has been shown on a camera later on in the night and the "digital enhancement" of said footage. When we get a specific timeline of the events, including when phones calls began and ended, and forensic evidence detailing how far away Zimmerman was from Martin when he shot, then we'll have a much better idea of what really happened.
Right now, Zimmerman is in custody because he followed Trayvon Martin because he thought he "looked suspicious," and then shot and killed the unarmed 17 year old. I don't care who you are or what you believe, if you think that it's improper for a person to be charged with second degree murder under those circumstances, you're crazy. You can't go around with a gun playing police officer and following anybody you deem suspicious. End of story.