On April 30, 1981, during a May Day music concert, Riocentro was the target of a terrorist attack by hardliner members of the Brazilian military dictatorship (1964–1985). Sergeant Guilherme Pereira do Rosário and then-Captain Wilson Dias Machado, nowadays a Colonel, were responsible for detonating two bombs at the venue. Around 9 p.m., however, one of the bombs exploded in the lap of Sergeant Rosário, killing him and seriously wounding Machado. A second bomb exploded a few miles away at a powerhouse responsible for providing electrical energy to Riocentro; it was thrown over the fence and exploded on the ground, and the electric power supply was never interrupted that evening. The government immediately blamed left-wing radicals for the attack. This theory had no support at the time of the event and nowadays there is strong evidence that the attack was planned by the hardline sector of the government to convince the moderate sector that the left-wing urban guerrilla was still active and that a new wave of political repression was required. This episode marked the decline of the military regime in Brazil, which would officially end four years later.