Didn't Trayvon Martin also 'Stand Your Ground'?

I'm a little confused by this Stand Your Ground law. "In the United States of America, stand-your-ground law states that a person may justifiably use force in self-defense when there is reasonable belief of an unlawful threat, without an obligation to retreat first."

So, how is it that George Zimmerman is using the Stand Your Ground law, to justify killing Trayvon Martin, because he said he felt threatened...so why can't Trayvon Martin use the same law because he most certainly felt threatened by some stranger going after him with a semi-assualt rifle? Stand Your Ground must be reciprocal, right?

Answers, thoughts....