Can someone explain this Zimmerman case to me?

I must say I’m surprised to hear so many people are happy Zimmerman was found not guilty yesterday. I don’t know a whole lot about the case, but I do know that this man killed a teenager and is now walking free because of politics. I know it’s mostly the conservatives and 2nd amendment nut jobs that are happy, but I’d still love to know why they think Zimmerman deserves to walk free.

I hear that he claimed he killed Martin in self defense after being attacked, and that he shot Martin with the teen’s gun, but he was later discovered to be unarmed. Is this true? If so, that one lie seems to poke holes in the self defense argument. Also, why would he take it upon himself to get out of his car and approach a boy walking in the rain? Especially when the dispatcher told him not to.

It seems so unfair that he’s free and Trayvon Martin’s family is left with no sense of justice being served.

I’m not a very political or even “tuned in” person when it comes to this stuff (I normally don’t care), but can someone explain this to me?