I'm probably wrong but it sounds to me that he may have been trying to commit suicide and sadly got his wish...unless somebody came up in his room, bashed his head in, walked out, and left no evidence I just find it a little peculiar.
Yes, head trauma is real and ain't nothing to play around with but a simple head bump isn't going to crack and shatter your skull into pieces and cause hemorrhage. He had too been repeatedly bumping his head until he went unconscious, fell asleep, and never woke up.