Yes, I understand that.
What is disturbing to me is that the flippant statement, repeated in most media accounts, that "Zimmerman was not arrested" gives the impression that police brushed off their hands, gave Zimmerman a friendly wave, and everybody called it a night. That is not what happened, and I think if most casual followers of the story were aware that he was cuffed and driven downtown while other officers and paramedics tried to revive Martin, they might have a different impression of that evening's events.
The police took him into custody, took away his gun (and still have it, contrary to many media reports,) roped off the scene for evidence collection, canvassed the neighborhood and took witness statements that night and in subsequent days, and have conducted lab work on physical evidence (not yet released to the public.)
"He was not arrested" has become some sort of shorthand for "the police didn't care why the black kid was dead and just took the white guy's word for it."
I maintain a healthy skepticism about law enforcement and official reports, but I also respect the fact that, despite mistakes, most of them try to do a good job, and I just haven't seen any evidence that they did not try to do that here.