Police innocent of murdering unarmed man? Al Sharpton arrested

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in a demonstration in protest of the innocent verdict for the policemen in the shooting of unarmed Sean Bell. I was appalled that they were judged innocent, but I wasn't there and I have no idea why they suspected he may have been armed. Here is the link to the story of the demonstration and arrests: http://www.reuters.com/article/domesticNews/idUSN0729934620080508 If it were my son, I'd be demonstrating, suing, and everything else I could to legally avenge him. But did they know of this man, did he have a record that made them think their lives were in danger? Was it because he was black and leaving a strip club? How could they escape any repercussions from killing this man?