Medical school is one of the most difficult experience anyone can go thru. Unfortunately it is also not uncommon for the stress and fatigue to unmask mental illness, encourage drug use, or other abnormal behaviors.
In my experience, people who fail classes due to poor academic preparation are usually well supported by school, to make up deficits over the summer and/or repeat the year entirely without judgement. Allopathic medical schools are generally considered to be “pipelines” meaning once you are in, you should get out.
BUT people who suffers mental issues, addiction, or loss of interest are different. Schools can’t “fix” these things. You best get him the MH he needs and see if he is fit to return in Fall. If he is deemed incompetent, you can get legal help to set up conservatorship or legal representation to communicate with school. He will not be the first, last or only student to have this happen, so school should already have some protocol setup to assist the student, someone just need to call and ask.