How we cite our quotes: All quotations are from The Shining.
Quote #1
ULLMAN: He ran amok and killed his family with an axe.
Mr. Ullman is no stranger to crazy. After all, he manages a hotel where one of the caretakers murdered his entire family with an axe. Ullman seems to think that the isolation of the hotel had a big role to play in the man's mental break.
Quote #2
ULLMAN: [He] stacked them neatly in one of the rooms in the West Wing, and then he put both barrels of his shotgun in his mouth.
It's possible that Delbert Grady killed his family out of frustration and that he was sane when he did it. But it takes a crazy person to stack his family up in little pieces and then kill himself. The dude never had any plans of getting away with what he did. He just wanted everyone dead.
Quote #3
ULLMAN: The police, they thought that it was what the old-timers used to call cabin fever.
Ullman mentions how the police thought that Delbert Grady had some kind of mental break because he'd been cooped up with the same people for too long. It's certainly a possible explanation, but not very likely once you see Grady's ghost wandering around the Overlook Hotel.