If a 6-foot person is sitting on your chest, beating in your face with his fists and you have a gun in your holster, are you going to let him kill you OR are you going to save your life?
The police made a determination based on evidence at the scene, on 911 calls and eye-witness accounts.
I suspect this whole tragedy could have been avoided if Mr.Martin had used common sense, stopped, and chatted with Mr.Zimmerman. Mr.Zimmerman has, as a member of community watch, a history of informing the Sanford police of questionable or suspicious activity in that gated community. He does not, as far as I can ascertain, have a history of violent confrontations, something community watch folks are warned against doing.
If you go to the City of Sanfords online site, the telephone calls are all there as well as a report from the City Manager, Norton Bonaparte
http://www.sanfordfl.gov/index.html
http://www.sanfordfl.gov/investigation/docs/Zimmerman_Martin_shooting.pdf
I think Doe Eyes would let them kill her or him.