Jonas was absolutely appalled when he watched the video of the release. He couldn't believe that release, which was portrayed as this wonderful thing, was really just killing. He was also devastated to find that his father had been doing this and lying to the family about it.
As he watched it happen, he felt like he was choking and he flashed back to the memory the Giver gave him of the dying soldier. Then he starts to cry and yell.
After he watched the video, he was so upset that he did not want to return home that night and spent the night with the Giver.
Once he calms down a bit, he starts thinking about how no one else in the community has feelings. It is at this point that the Giver starts to think about having Jonas escape from the community.
In the book "The Giver" Jonas witnesses his father take and weigh twins. The larger twin is cleaned and sent to be dressed. The other twin, although he is only a tiny bit smaller, is chosen to be released. Jonas is relatively unaware of what will occur. He thinks that his father is giving the infant his shots. His father injects a chemical into the infants fontal. The infant cries very hard and then dies. Jonas does not fully comprehend that the infant has been killed until he sees it put into a box and dumped away like garbage.
Jonas is devastated and angry. He does not understand how his society can end a life and dispose of it like garbage. Jonas was willing to hold the memories of the people. However, his witness of the release is the turning point for Jonas. The rest of the story progresses because of his new knowledge.