Character-What events trigger such change.

When Jack took control of the hotel he start to act weird due to the
spirit of the previous caretaker who became violent and crazy.
Jack had became obsessed with writing and the boiler room was of limits and that had to be refill every day. If he had forgot about it it would over boil and explode.Mean While Jack would continuously write but they weren't like the things he had previously wrote.
These were horrible things about hate and he keep repeating himself.
Eventually Jack loses himself to the spirit an tries to kill his family.