Argala and his group began plotting to kill Carrero Blanco instead, in what would be known as Operación Ogro. The Commando Txikia also considered other options: killing Manuel Fraga, killing Alfredo Semprún and breaching the walls of the Segovia prison to break out anti-Franco prisoners. On 25 September, they attacked a government arms store to obtain explosives, scattering propaganda of an invented revolutionary group as a distraction. On 20 December 1973, posing as workmen, members the cell triggered the bomb that went off in a tunnel under the Madrid street as the car of Carrero Blanco passed by on his way home from Mass. Franco's right-hand man initially survived the attack, though he later died in hospital, while his chauffeur and bodyguard were also killed. Argala was the only able to identify the mysterious man who gave Carrero Blanco's schedule and itinerary to ETA.