Quoting GavinsMomJohnnysWife:" Maybe he feels bullied? It's normal for a child to have emotions, but he knows right from wrong."
Kids will act out like this when they feel helpless. It sounds like he's trying to gain some power, some control over his life. Not saying it's acceptable, this behavior isn't at all but kids need to be taught the appropriate way to gain some control and be allowed to have some control over what happens to them or they will lash out like this.
I noticed you said that your 8 year old "pantsed" him as a joke. Imo that's not a joke and I wouldn't let my 8 year old think it was. Maybe he felt embarrassed after that. What did you do when your 8 year old did that? I think the pee thing is odd and not normal but that might have been in his mind a way to regain control over the situation and defend himself (not that it was right, I'm not saying that).
If you think he has a disorder then I would definitely look into that but I don't necessarily think this behavior means he does. I'd address every other area first though. Make sure all of his basic needs are being met. Does he eat healthy, does he watch too much t.v. or get too much screen time in general, does he play outside everyday to get his energy out, do you have the kids do activities together, do you spend time with him everyday connecting etc. Once all of those basic things are addressed if he's still acting like you described then I would consider that it's a behavioral disorder. Imo the basis to good behavior is a good connection. Not only with you but with his siblings. If he has a good relationship with you then he will have a natural desire to do what you ask (not that he won't still act age appropriately but he will be more inclined to cooperate). If he has a good relationship with his siblings then he will have more empathy for them and not want to do things that hurt them (again, there will be age appropriate behavior but not things like throwing pee at eachother). Just some suggestions, not saying you do or don't do these things already or haven't addressed them. :)
If you're interested a great website is http://www.ahaparenting.com/. You might find a lot of good tips for what you're dealing with on there.
Quoting Cassi♥DLKA♥:" Thanks! I will check out the site. I wasn't here when it happened, I was at work. My SO called me ... [snip!] ... (Not being defensive, sorry. My mom already tries to make me feel bad enough about having to work...it's a natural response.)"
Don't be sorry. :) I definitely understand that.
Sorry to hear you are having these issues. I cant really weigh in on if I think its a disorder or just really terrible behavior but its definately out of the ordinary enough to make a log for a few weeks and show the peditrcian and go from there. I hope he gets the help he needs..:oops: