@Monday55
I don't think he has aspergers too...People with AS are usually introverts, who don't like talking and usually have a few friends to zero friends. Not mentioning they also tend to have a very high IQ
Actually this is my experience. Of course it's not 100% rule, but I've come across a lot of people (and had perfectly well functioning successful friends) with Aspergers of some level or another and this describes them exactly.
Friends - this was very mild aspergers, barely noticeably until they said something and then a few things made sense. Not so much introverted as a little nervous other people won't like them, do join in, have friends and are social, but a bit nervous rather than confident, even if they don't let this show. Also able to function well without need to be surrounded by people, so that may seem introverted, but in fact it's just happily going along with whatever the situation happens to be. Plus yes, high IQs.
For the shouting - how is his hearing? I had a friend who used to speak incredibly loudly, the larger social group commented not to his face which I didn't like, so when one day when he was talking to me, because he was shouting too loudly for where we were, said "You're speaking quite loudly for here, do you think it's ok?" He told me that he was partly deaf in one ear and that's why he spoke so loudly, he knew because he had been told but couldn't regulate it easily... it's like wearing headphones and talking at the same time, you shout over the music because you can't hear your own voice well enough.
So maybe a hearing check?
Definitely a diagnosis, whatever it is, will help for work. Adjustments can be put in place to assist him and if there are related challenges, he won't be unfairly punished.