re: Ferguson Protestors Cause Car Accident While Charging The Street and Blocking Rd

Question - I've heard of parade permits being issued for legal reasons but I've never seen any legalese about protest marches and/or assemblies on public property. If roads and streets have not been cordoned off for such activities then I would assume that protesters are basically jaywalking. If jaywalking laws are in effect and some of these people are breaking this law, then is it a non-criminal event when a protester is run over and possibly killed? I know there are usually clauses factored in concerning "avoidable accident" but if not avoidable then what will be the reasoning for any criminal charges from either party involved in the accident?