Read more closely. They were shown an edited video which cut out the time of the shooting. This allowed the actions of the victim to be described in terms far more threatening than they were, while portraying the barked orders of law enforcement as far less confusing than they were.
As a juror, and as a citizen my assesment is that the editing constitutes evidence tampering.
Assuming this is an un-editted snippet at post #65, you can see that the kids hand comes forward - empty - BEFORE the cops starts shooting.
http://freerepublic.com/focus/news/3612704/posts?page=65#65