A bridegroom gunned down his new wife, his best man and then himself after announcing to horrified guests that he had a "surprise" for them.
Witnesses reported that 29-year-old sales manager Rogerio Damascena did not give any previous indication that anything was wrong at his wedding reception in Rio de Janeiro, police investigator Joao Brito said.
Mr Brito would not speculate on a possible motive, saying family members were in shock and he had not interviewed them yet, but said the killings were believed to be premeditated because the groom had hidden a gun in his father's pick-up truck.
Twenty-five-year-old bride Renata Alexandre Costa Coelho and best man Marcelo Guimaraes were killed in Saturday's murder-suicide. A brother of the bride was treated at a hospital and released.
The Globo.com website quoted a sister of the bride who left before the shootings as saying she did not believe it was a crime of passion.
"My sister was a wonderful person who loved and wanted to be loved," Lucia Helena Coelho said.
"He was happy, she was happy, the party was beautiful. His family adored her and doesn't understand this.
"He revealed himself as a sociopath who fooled the entire family and killed his best friend, who was ... the best man."