What are they protesting?
Because they think the kid that was shot and killed was done so over racist pretenses.
The reality is that: 1) its a tragedy this kid died, 2) no one knows (yet) if this kid was mouthing off and deserving of restraint or surrendering, and 3) no one wants to let the justice system apply penalty where its due before they convict the accused (on both sides) in the court of public opinion.