Jack had promised to protect the humans of Apocalypse World. When one of them had been killed, he went crazy. He went after the first person with any connection and almost killed him. The man was innocent, but Jack was blinded with grief. When his father, Castiel, tried to stop him, he had hit him and knocked him aside. He didn't release the innocent man until Dean literally shot at him. Jack was extremely hurt by that, though, not taking it well at all. He teleported to a random place in the woods, just wanting to get away.