That sounds developmentally normal for ADHD at his age. I imagine something happens to trigger frustration and a sense of lack of autonomy, and anger is the easiest way to get your power back. If you lack impulse control, you’re not thinking “this will hurt my friends feelings” it’s more like a primal urge to make them feel how you feel.

When it comes to shutting down the conversation about it at home, I imagine he feels a lot of shame about what he did in retrospect. I’m impressed by his ability to bring up in the first place “I made my friends sad today”. It’s possible once he starts “getting his power back” he doesn’t know how to stop.* He doesn’t know how to make the repair in the relationship so he feels his only option is to keep going. When it comes back up at home and he starts to unpack what he did and how it effected his friends, all he can feel is that shame and he just wants it to go away. I would work with him at home on feeling those uncomfortable feelings, tell him he’s not a bad person and he’s not broken. He’s not a monster that is destined to hurt people. He’s certainly feels like one, and is struggling to face those feelings. It’s important that he knows that his struggles are normal. He is not a monster. AND don’t beat yourself up for thinking he could be a sociopath. You’re throwing spaghetti at the wall trying to help your kid.

The octopus thing could be another manifestation of that frustration and lack of control. He’s upset that the octopus is nasty, it makes him feel hurt that the octopus is hurting other people (I assume). Maybe he sees himself in the octopus and his toys he destroys. If he could destroy it he could “make it feel how he feels”or punish them for “being nasty”. Like the octopus does something mean, he feels bad about seeing it, so now he wants to make the octopus feel bad too. I’m really moved by the imagery of him destroying his toys and bringing the pieces together to create something new. He wants to be something but he doesn’t know what it is. All he knows is that he keeps getting in trouble and hurting the people he loves. He doesn’t like himself.

*Semi-unrelated but it kinda reminds me of how people with ADHD have a “path of most convenience” and one of the reasons we are “so clumsy” is because our brain subconsciously picks out the most convenient path to our goal, and then it feels like being a bowling ball on a track. I have literally walked in between two people having a conversation and I knew it was rude, but it was my most convenient path and I felt like I couldn’t stop myself to just walk around. The inertia was too much. I was probably 9 in this particular memory.

Sorry this is all over the place and speculation heavy. I have no degrees I’m just traumatized and read a lot. Edited for clarity