Caught my 2 boys masturbating there are 11 and 12
I don't think you have to jump to the conclusion he was molested.
Kids, they sometimes do crazy stuff out of the blue, that's why when we catch the inappropriate behavior we correct the behavior lol.
I think a firm, short talk should do it.
i know how you feel. my 6 year old son, had do this by himself for a couple of months. even after reporting it, my son had continued. we recently found out that his bio-father have molested him. in feburary it would be a year that he has been ina "safe home". your situation could be worse. as for mine he didn't understand that it was wrong for him to do. yes, a councelor will help but, in some cases there is no garentee that it will not happen again. good luck on getting it straight before it gets worse.
I don't know about him molesting other children, but he is 12 and should know better. I would not leave him unsupervised. He may have been molested himself. Or maybe he just thought it was funny to do it in front of his two sisters. You need to talk with him further or get him a counselor if he isn't sharing more with you.
Good luck...sorry about that--it's a sticky situation. I would be mortified if my girls saw that.