The Estadio Nacional disaster of 24 May 1964 (also known as the Lima football disaster) is, to date, the worst disaster in association football history. It occurred during a game of Peru versus Argentina. During the match, there was an unpopular decision given by the referee. Outraged, the Peruvian fans decided to invade the pitch. Police retaliated by firing tear gas into the stadium crowd, causing a mass exodus. The deaths mainly occurred from people suffering from internal hemorrhaging or asphyxiation from the crushing against the steel shutters that led down to the street.