Can i sue someone who is mentally retarded?

A kid was walking down the street with a stuffed teddie bear. He is retarded or something. he was actually talking/singing to it! It kind of annoyed me so as he ped by i stuck my foot out and tripped him. He ended up breaking out most of his front teeth on the sidewalk. I was laughing so hard i just grabbed the teddie bear and ran, which made him cry like a baby. Well, the cops found the teddie bear in my garage and now his family is suing me. Is there any way i can countersue for him being a public disturbance or something?