Behavioural issues - what could be wrong?

So this is my husband's coworkers son. He's always talking about how aggressive his son is, how he gets in these moods where he's just a monster and then at other times, he's worlds sweetest child.

He's on a host of medications that they've just "upped" but from my side, I'm worried that it's no good continuing to increase medications with no proof they're actually working and no actual diagnosis.

They don't know what's wrong with him that he's like this, he's been in therapy for years and it's so bad that he can't even go to a regular school, they have to get a full time tutor because this child is forever threatening to kill (literally kill) the teachers, the other kids as school, physically assaulting them (yes, even the teachers)... I also want to note this child has never actually been disciplined either. He breaks TVs, throws tantrums that can rival toddlers, he's out of control. And he's only eight years old.

My, obviously primitive brain, thinks he might just need good discipline, punishment because no one is actually teaching him not to do these things, they just send him off to the psychologist to adjust his meds when he gets bad.

So I thought maybe someone here might have an idea what might be the problem with him so they can get him under control?

EDIT: Wow. Talk about jumping to some conclusions here! The father is at his wits end here, he's considering leaving his son at a home because he not only can't afford a private tutor, but he also can't deal with the stress of having this child. I posted to try help, to try see if there's something that maybe someone has overlooked. I'm not being nosy or stuffing my nose in other people's business. This poor man is on the verge of a nervous breakdown and is constantly reaching out to us for help.