From your brief description it's hard to say, however he may very well have a condition such as ADHD, or something on the autism spectrum. Eg, if you notice that he can't seem to regulate his behaviour and that his reactions to certain situations seems extreme ( like way over the top), he really struggles to form friendships, can't handle change, can't talk about his feelings or explain why he reacts this way etc, etc ( the list of symptoms for these conditions is quite long and it would really take an expert in this field to give a definite answer!). People with these conditions are often left un-diagnosed and therefore given no help, and because their behaviour can be so challenging they are often judged harshly and end up, as you say, getting into big trouble.
May I suggest that your family finds out more about this, I'm not saying it's the answer but clearly his behaviour is not acceptable and he needs to find a way to manage himself better. There's lots of info online about autism and ADHD, maybe take a look and see if any of it looks familiar- thinking back from what you remember about him as a child too.
One more thing- if his character has changed recently, like he was fine before- then it is likely that something has happened to cause this, that he can't explain easily and is hard for him to talk about. For example, when my daughter was this age, she suddenly started lashing out at me, going between very withdrawn and not talking to screaming abuse, hitting out and smashing things like her laptop. It took me ages to get out of her that she was being badly bullied at school ( physically and emotionally), once she told me we were able to sort it out with her school and gradually she recovered and got back to her normal self.