What happen to Ralph at the end of the chapter 11?

Piggy is crushed to death by a boulder dislodged by Roger. The group falls into a sudden and deep silence. Just as suddenly, however, Jack leaps out of the group, screaming deliriously. He shouts at Ralph that "that's what you'll get" for challenging his authority, and he expresses happiness that the conch is gone. Declaring himself chief, Jack deliberately hurls his spear at Ralph. The spear tears the skin and flesh over Ralph's ribs, then shears off and falls into the water. A terrified Ralph turns and runs, spears now coming at him from different directions. He is propelled by an instinct he never knew he possessed. In his flight, he catches sight of the headless sow from the earlier hunt. After Ralph departs, Jack casts his gaze on the bound Samneric. He orders them to join the tribe, but when they request only to be released, he bullies them, poking the twins in the ribs with a spear. The other boys cheer him on but fall silent when they notice Roger edging past Jack to confront the twins.