My son used to do that , now he just does it to his older brother, not that it is ok, but saying that he has come a long way. That can stem from the SPD whole picture! He doesn't know what ot do so that is how he reacts. You need to get a sensory diet in play. He needs to know there are boundaries! Visual aids are great! A visual punishment chart, do not be leary around him. He needs to know that you are in charge, he just needs the tools to help him cope within his body. He is in pain, it is very hard to comprehend, but he is in actual pain. We may not hear the sounds he hears that sets him off, we may not feel the same scratchy clothes that are irratatring him and they would not us, he does not know how to express what he is feeling. So once yo ufind out what it is that really gets to him. Watch his behaviors, does he hold his ears a lot, is he picky with materials, for example, my son will NOT wear denim! He lives in "soft pants' as he calls them. He is a sensory seeker, he used to jump across the concrete on his knees! I got a indoor trampoline, I made him a weighted blanket, he has a sit fit cushion at school, as he grows his needs change. The meltdown stems from something that is bothering his sensory system. He has had enough, teasing can cause it, lights, too many people, noises, etc.... frustration, transitioning, all of it! So keep an record mental or on paper and watch for patterns. Does he melt down right before we have to stop and do something else. If this is the case a timer can help, discussing what is going to go on, a calendar for him, etc... I know that I have to give warnings before something is going to be finished. "You only have 5 min left" he can tell time now, but before I would set a timer. All these things are very important in their world. But always to remind that tings can change and don't always happen per schedule. A punishment I also use is pushups, there is a thread on here where we talked about it. It is great deep pressure for them! SO the aggression might come on during or after the meltdown?!?!? Try and figure out what is causing the meltdown to happen, then go from there. But do not walk on egg shells, yo uare in charge, you are the one who sets the rules, you just want to help him learn how to use the proper coping skills and act appropriately! Read a lot of what the adults put, it helps to put you in your child's shoes and know what they are feeling! I always put myself in his shoes, it helps me to better help him and try to understand what he is going through.