killing the secretary Lyda Monteiro da Silva. On the same day the offices of Rio de Janeiro city councillor Antônio Carlos de Carvalho were destroyed. Timeline Throughout the evening of 30 April 1981, the Riocentro convention center in Rio de Janeiro's West Zone hosted a pop music concert organized by Centro Brasil Democrático to celebrate Workers Day. Over 20,000 people were in attendance, and the event was headlined by many famous MPB artists such as Moraes Moreira, Alceu Valença, Gal Costa, MPB-4, Beth Carvalho, Gonzaguinha, Elba Ramalho and Chico Buarque. On the afternoon of 30 April, Army Colonel and commander of the Rio police force Newton Cerqueira made a phone call to Lt. Col. Fernando Antônio Pott telling him to suspend policing of the Riocentro event for the evening and to keep 60 officers at the precinct alert for any emergency. At Riocentro, operations manager Maria Ângela Lopes Campobianco reassigned Lt. César Wachulec from head of security to the tickets office, claiming he had issues with alcoholism. Outside of Riocentro billboard were graffitied with the acronym VPR (Vanguarda Popular Revolucionária, a left-wing guerrilla group that had not existed since 1973). At around 9 pm, two cars were driven into the Riocentro parking lot, one of them a Puma GTE. In the Puma were two DOI-CODI officers, who planned to detonated a bomb under the stage of the concert. At around 9:15 a bomb went off prematurely in the car, killing Army Sergeant Guilherme Pereira do Rosário, and seriously injuring Captain Wilson Luiz Chaves Machado. Machado was taken to Hospital Miguel Couto, where he requested that Captain Francisco de Paula Sousa Pinto be informed of the accident. Machado underwent surgery all night; according to an early medical report his condition was serious but not life-threatening. At 9:45, another bomb detonated at a nearby power station; the bomb was intended to cut off the electricity provided to Riocentro. Minutes later a Chevrolet Opala left the parking lot, with one of the passengers exclaiming to a security guard, "you haven't seen anything yet. The worst is going to happen in there". The bomb failed to cause a blackout. Police surrounded the area where the bomb exploded. Agents from the General Department of Special Investigations (DGIE) and the Political and Social Police (DPPS), as well as officers from the 16th and 32nd precincts, inspected the location. Forensic expects of the DGIE and DPPS concluded