My son is 12yo and has autism. I completely understand unexpected behaviors. Last time he came out WITH supervision he tried to bop the rooster (who just got too close to him). I would keep a close eye on your son and keep talking about the importance of waiting for momma and daddy to come with to visit the chickens (a social story may help a lot). Also, I would make sure anything he can get into is locked up and out of reach. Unfortunately, you can't monitor 24/7 and sometimes even though we think they're "doing great" or "wouldn't ever do that" they like to surprise us.