Can a mentally retarded person be charged with a crime if they assaulted me?

So the other day my mom and I were in the store and ahead of us in the checkout line were a large man and a small woman. i didn't realize at the time, but the man was retarded (i don't know if it was downs or severe autism, i didn't look at his face) and started freaking out. the woman tried to control him but she couldn't, so she led the man down out of the line and as she did, the man slammed both me and my mom against the checkout belt thing. it hurt a lot, but we didn't do anything since it's one of those situations where even if you are right, people will still hate you and say you're wrong
this isn't the first time something like this has happened (the downs box boy once told my mom to die because she declined help out to her car). both of us are sick of it. my question is, if something like this should happen again, some sort of violence or assault, could we press charges? if it were a normal person i know we could, but are the retarded not responsible for their crimes? is it like a dog bite case where the dog isn't convicted but the owner/handler is for not being in control? i'm sorry if my language is insensitive, but i want to be clear and tiptoeing around what i'm trying to ask won't help.