Federico Miguel Sierra was an infantry major, working in the general staff. He was 37 years old and had taken part in international missions in several countries, including Yugoslavia. He lived in Alcalá de Henares (Madrid) with his wife and three-year old son. Each morning, he took the train to work in Madrid city. Federico’s father was the military governor of Navarre. When he was unable to contact his son, he left immediately for Madrid. His worst fears were soon confirmed.
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.