Tempered glass doors sometimes can shatter violently. It only takes a slight flaw, a break, a scratch or an imperfection.
Ours burst with a roar about ten minutes after going to bed. Nobody was in the bathroom and the door was shut. It may be relevant that the central heating had gone off so the house was cooling off into the night. Nobody used the shower for at least 12 hours and we’re not aware of any damage that could have started this.