New Video of George Zimmerman at the Police Station

From ABC News:

A police surveillance video taken the night that Trayvon Martin was shot dead shows no blood or bruises on George Zimmerman, the neighborhood watch captain who says he shot Martin after he was punched in the nose, knocked down and had his head slammed into the ground. 

The surveillance video, which was obtained exclusively by ABC News, shows Zimmerman arriving in a police cruiser. As he exits the car, his hands are cuffed behind his back. Zimmerman is frisked and then led down a series of hallways, still cuffed.

You can see the video at the site. I don't have much to say here. He doesn't look like someone whose had their head bashed into the concrete. But perhaps I'm missing something.

Also, Trayvon Martin's parents offered the official explanation given by the Sanford police:

According to Tracy Martin, the Sanford, Fla., detective recounted this sequence of events: Trayvon Martin walked up to Zimmerman's vehicle and asked why he was following him. Zimmerman denied following the youth and rolled up the car window. 

Minutes after Trayvon walked away, Zimmerman got out of his vehicle. Then came the second encounter, according to Tracy Martin's recollection of the detective's account. Trayvon Martin appeared from behind a building in Zimmerman's gated community, approached him and demanded, "What's your problem, homie?" 

When Zimmerman replied that he didn't have a problem, Martin said, "You do now." The unarmed teenager hit Zimmerman, knocked him to the ground, pinned him down and told him to "shut the [expletive] up."

During the beating, Zimmerman pulled his gun and fired one shot at close range into Martin's chest. "You got me," the teenager said, falling backward.

This smells to high heaven. What I can't understand is why the police would offer this explanation, given that it's directly contradicted by the 911 tapes. What, precisely, is going on with the cops down there?