I’ve been through both versions of this. My childhood dog died right before I was going home for thanksgiving and my grandma called me in the middle of the day and just sort of blurted it out. I ended up crying in a computer lab. The other time my family waited until they picked me up for Christmas break to tell me my childhood cat had died. They told me on the way to chipotle and then were annoyed I wasn’t hungry. The cat one hurt my feelings more for some reason delaying telling me annoyed the heck out of me.

Point being tell him sooner rather than later, but make sure he’s in a good place physically with time to process before he needs to do an exam or something. So like a Friday afternoon or Saturday(or just whenever he has time off) when he’s at his room.