Can Inmates in the SHU Receive Mail or Make Calls?

The SHU, the hole, solitary confinement, they are all the same thing, and being placed there does not cut off contact with family entirely. Mail continues normally in both directions. He can send and receive letters on the same schedule as general population. Phone access is restricted though, typically down to one 15-minute call per week. Visitation depends on what he did to land there. Some offenses allow visits to continue, others result in visitation being suspended for the duration. He will know which applies to his situation.

On finding out why he is in there: the facility will not tell you. Staff are not going to share disciplinary information with family members, and privacy rules give them cover to say nothing. The only person who can tell you what happened is him, either through a letter or during that one weekly call. If visitation is still permitted, he can fill you in in person.

Keep sending mail in the meantime. It still reaches him, and during a stretch in solitary, getting letters is one of the few things that breaks the monotony.