The crowd is shouting and throwing things, first bread, then cushions and wine bottles. The bull becomes exhausted from so much stabbing and lies down. Finally someone kills it. The crowd rushes into the stadium. Someone cuts off the bull's tail. A child steals it. The narrator sees him later at a cafe. He has no remorse.
This passage extends the metaphor of bullfighting as war. The fighters tired out the enemy (the bull) and then killed it. Once it was killed, which symbolizes the other army being defeated, the audience (the civilians) tries to profit from the result as well.