What is the climax in the book The Giver?

As the Receiver, Jonas has access to memories that are shared with him by the Giver. Jonas is also allowed to follow a different set of rules than other community members. For example, children are not allowed to witness the "release" of a new child. Jonas is an exception to this rule. However, since the release of a new child by Jonas' father already took place earlier that morning, the Giver explains to Jonas that he can watch a recording of the release.
Jonas knows his father to be a gentle man, and he hears the "gentle voice" that his father uses with the baby. He watches as his father prepares a syringe. Jonas remembers that babies receive shots, so while he is worried that the baby will experience some discomfort, he isn't especially alarmed. However, he notices that his father inserts the needle in the soft spot on the baby's head. As Jonas watches, the baby becomes limp and dies.
The climax of The Giver occurs as Jonas becomes aware that his father has killed the baby, leading him to begin a new course of action. It is painful for Jonas to realize that his father has been lying about what happens during the release of a new child. Feeling a "ripping sensation inside himself," Jonas and the Giver make a plan.