I watched reports on this earlier today. What I do not understand is why they have not simply had him charged with assault. The kid, autistic or not, is a risk to the neighbors.
Lots of things can be done here, without filing a suit. File a complaint with the police, get a restraining order from a court, call child protective services. Social services, would probably see this as an emergent situation and get the family some help with the child. Lots of ways to do it without giving a couple lawyers a pay day.