The attackers were not finished. Josimar de Sousa, the man who had shared beers with Marçal, stabbed Cantanhede in the throat, the police said. He fled and was believed to have left Maranhão.

Francisco Edson Morais de Souza, Luiz’s brother, came from his home, carrying a sickle with a curved blade. Both brothers had been charged with burglarizing houses and pickpocketing, but had not been convicted, the police said. A family photograph of Francisco, 32, showed him with a trim mustache and a nose that seemed to have been on the other end of a fist.

He was widely described as a heavy drinker and user of drugs. On this afternoon, the police said, Francisco was “completely out of his mind.” He swung his sickle at one man on his way to the field. He shouted. He warned that he would kill anyone who got in his way. He beheaded Cantanhede, the police said, and tried to quarter him.

Teresa Ferreria, 52, a farmworker who lived adjacent to the field, saw Francisco holding Cantanhede’s head like a trophy. She was afraid to leave her porch. Francisco placed Cantanhede’s head on a post on a barbed wire fence, the police and witnesses said. Then Francisco left. One man saw him sitting in the middle of the road.