in his statement, the Prosecutor McCulloch didn't exactly make a case for a no-bill.. if I'm a potential rioter, I would take hold of these words... that Brown was shot in the front 6-7 times, from a distance.. and that followed several shots at close range by the squad car, after which Brown ran from the Officer..
it was never stated how close Brown was during the second round of shots, but the conclusion was that Brown must have been headed towards the Officer, based on the angle of the final (Believed to be final) couple of shots..
my take is the Grand Jury didn't conclude the Officer was justified, but it could not conclude that he wasn't... too many holes in the conflicting stories that couldn't be reconcilled.