I wonder about that too, Bella. I have known more than one person to get VERY odd while working on their thesis or some of the more difficult portions of their advanced degrees. If he already had some mental illness (Perhaps something like schizophrenia which can be very dormant for a long time) and then had a psychotic break, I can see something like this happening.
Lately I've been very concerned for a friend of mine who is an instructor at a prominant university and has been receiving unplanned visits from a homeless man who was initially diagnosed with his paranoid schizophrenia there and thus blames the university for his difficulties. She's now on first name basis with all the campus police and has a panic button in her office
I'm sure at some point he was someone's 'promising student' neighbor or son as well.