Souper, detained under the Allende administration and under prosecution for sedition in a military court, was released following the successful coup on September 11, 1973. He then became an agent for the Santiago regional intelligences services (División de Inteligencia Regional de la División de Inteligencia Metropolitana). Though declassified CIA documents do not identify any American involvement in the tanquetazo, Souper was named by the CIA as early as August 1971 as one of eight known officers predisposed to oppose the government of Salvador Allende.