Domnino Simón did not normally take the train, but on the morning of 11 March, 2004 his car was not working and so he went to Santa Eugenia station to take the train to his work at the Mutua Madrileña Automovilística insurance company. He was travelling with his wife, Cristina López Ramos, with whom he had two children, aged eleven and four. The couple were both killed in the explosions at El Pozo station.
11 March 2004 fell on a Thursday. Early that morning, a number of terrorists with links to Al-Qaeda planted thirteen bombs on four suburban trains covering routes running through Madrid. Ten of the bombs exploded between 7.37 and 7.39 am, when the trains were at Atocha, El Pozo and Santa Eugenia stations and alongside Calle Téllez. 191 people were killed in the attack and around 1,500 were wounded. It was the deadliest terrorist attack in Spanish history. On 3 April 2004, agents from the Special Operations Group (GEO) were about to enter an apartment in Leganés where the perpetrators of the attacks were believed to be hiding when the terrorists detonated twenty kilograms of explosives in an act of collective suicide. The ensuing blast killed one of the officers, bringing the total number of people killed by the 11 March bombers to 192.