"He murdered his little girls with a hatchet, his wife with a shotgun, and himself the same way" (1.60).
Things get really violent, really fast in The Shining. Jack learns the fate of the previous caretaker, Charles Grady, and his family. Being a reasonable man, Jack doesn't let this bit of information dissuade him from taking the job at the Overlook.
(Danny with his arm in a cast) (2.45)
The memory of Jack breaking Danny's arm haunts both Jack and Wendy constantly. However, Danny is much more worried about the possible breakup of his family than he is about Jack hurting him again.
"Your Daddy hit George to make him stop cutting the tires and George hit his head" (2.46)
In this early passage, we get the idea that Wendy is making excuses for Jack's violence. When we know her better we learn this isn't the case. She just knows how much Danny loves Jack and doesn't want to say anything bad about him to Danny. Ironically, this is precisely what Jack accuses her of doing when he first becomes violent with her at the Overlook.