ULLMAN: He ran amok and eh... killed his family with an axe.
Ullman doesn't like bringing it up, but he feels like it's his duty to tell Jack Torrance that one of the hotel's former caretakers lost his mind and killed his whole family. Jack doesn't seem too concerned, but we all know that he definitely should be.
ULLMAN: Good. Glad you made it before they shut down the kitchen. Is your family having a look around? JACK: No, my son's discovered the games room.
At this point in the movie, Jack still seems pretty happy go lucky about his new job and his family. However, we can already tell something's wrong by the way Jack always acts more nicely to strangers than he does to his wife and son.
ULLMAN: Yes, very cozy for a family, and if you feel like spreading out you have the rest of the hotel to move around in.
Ullman is conscious of the fact that Jack will bring his family with him to live in the Overlook Hotel. He's especially concerned about how the family will live through the harsh winter months in total isolation. After all, experience has shown him what can happen to a family in these conditions, and it ain't pretty.
HALLORANN: Well, look sir, I hate to put you to any trouble, but there's a family up there all by themselves with a young kid, and with this storm and everything.
Hallorann might seem like he's just concerned about Danny and his parents because of the storm. But the truth is that Danny has used his mental powers to warn Hallorann that something terrible is going on with his family.
WENDY: You son of a b****! You did this to him, didn't you?"
It doesn't take much to convince Wendy that Jack is responsible for the bruises around Danny's neck. After all, Jack has a history of hurting the kid. Plus the fear and isolation of their situation is putting everyone on edge to begin with, so it's no wonder why Wendy would look for the simplest possible explanation. The alternative is believing that a ghost strangled Danny.
JACK: I haven't laid a hand on him. Goddam it, I didn't. I wouldn't touch one hair of his goddam little head. I love the little son-of-a-b****.
Jack is sick and tired of having his previous mistakes held against him and he hates that Wendy would be so quick to blame him for their son's injuries. And to show how upset he is, he decides he's going to murder both of them. Or something like that.
JACK: I'd do anything for him. Any f***ing thing for him.
Jack truly believes that he loves his son more than anything in the world. It's almost as if he can't feel the murderous rage building inside him. Or maybe, just maybe he thinks his family will be together forever if they all die together.
GRADY: Did you know, Mr. Torrance, that your son... is attempting to bring an outside party into this situation? Did you know that?
Delbert Grady becomes a sort of ghostly advisor to Jack as the movie goes on. The problem is that most of his advice tends to end with a demand that Jack murder his family.
GRADY: Your son has a very great talent. I don't think you are aware how great it is, but he is attempting to use that very talent against your will.
As a ghost, Grady seems aware of whenever other ghostly stuff is going on. That's why he gets so concerned when he senses that Danny is using his shining skills to call Mr. Hallorann to the hotel.
GRADY: But I corrected them, sir. And when my wife tried to prevent me from doing my duty I corrected her.
Delbert Grady is proud of his track record, which includes killing his family with an axe. In his mind, though, this was nothing more than his duty as a father to "correct" his family when they did things he didn't like. Well that's certainly a light way of putting it, Dad.