Then, a twist: The killers said it was all a game, and the penalty for losing was death.
When they were arrested on May 13, Ronald Ribeiro Rodrigues, a 22-year-old glass worker, and Mayderson Vargas Mendes, an unemployed 21-year-old, confessed to the murder of 21-year-old physics student Tiago Guedes and his parents, Douglas and Heloisa, in Guarapari, a seaside city of 230 miles northeast of Rio de Janeiro.
They said the killings were part of a role-playing game whose rules required the loser to let the winners kill him and his family.
"The suspects are very cool about what they did. They know what they did was wrong and that they will have to pay," said Espirito Santo state police inspector Alexandre Lincoln Capela.
"But I believe, from what I have seen, even going to prison is part of the game for them."
The case drew national attention and threw a spotlight on the subculture of role-playing games, which often employ occult imagery. Legislators in Espirito Santo state hastily introduced a bill to ban the games, and priests and pastors across Brazil penned sermons denouncing them.
"We must put the brakes on anything that encourages violence in our state," said Espirito Santo state assemblyman Robson Vaillant.
But some experts on the games have cast doubt on the killers' stories, saying their account doesn't fit with the traditions of such games -- the best-known of which is Dungeons & Dragons --- in which players assume characters and develop stories within the boundaries of elaborately defined fantasy worlds.
Rodrigues' mother told reporters she had never heard of role-playing games and that her son never played them.
And on Web sites and bulletin boards devoted to role-playing games, enthusiasts argue that the crime was a simple robbery and homicide, and the suspects are blaming the game in hopes of escaping punishment.
By claiming the family died as the result of a game, the suspects are entitled to a jury trial in which they are expected to plead temporary insanity. If they had confessed to robbery and homicide, a judge would have sentenced them. Brazil has no death penalty.
The case had parallels to the 2001 slaying of an 18-year-old woman, who was stabbed to death in the colonial city of Ouro Preto. Police claimed she had been playing a game over three days that included a bet that the loser would die. No one has been convicted.
But police said the game that left the Guedes family dead lasted only five hours. Guedes assumed the role of a policeman named Flavio, Mendes played a demon and Rodrigues was the wizard who ran the game.
Police said it wasn't clear how Guedes lost, but when he did, the players went to the bank where Guedes cleaned out his account, withdrawing $1,745.
Guedes then helped the two others to tie up and drug his elderly parents, Douglas and Heloisa, and watched as both were shot in the head. Finally, he was subjected to the same fate.
The suspects stole a computer from his house before leaving, police said.
To enthusiasts of role-playing games, the police version is full of holes. They say games can last for months or years and that there are no winners and losers, and never any betting.
Rodrigues and Mendes were working-class men who had known each other for more than 10 years and met the middle-class Guedes only on the day of the killing.
It seemed more than suspicious that Guedes was the loser, and that they were playing at his home with his parents there to watch.
Rodrigues' mother, Lucimara Rodigues Ribeiro, told the local newspaper A Tribuna that she had never heard of role-playing games.
"My son never played them at home," she said. "He's a good boy, and never behaved strangely."
But in an interview with the same newspaper, Rodrigues said he became so caught up in the game that he didn't actually believe the victims would die.
"When you create a character it seems like you're in a real game -- like you're in a forest, in the middle of lots of beasts," he said. "The game's not over. We're going to continue playing."