The FBI also spied upon and collected information on Puerto Rican independence leader Pedro Albizu Campos and his Nationalist political party in the 1930s. Abizu Campos was convicted three times in connection with deadly attacks on US government officials: in 1937 (Conspiracy to overthrow the government of the United States), in 1950 (attempted murder), and in 1954 (after an armed assault on the US House of Representatives while in session; although not present, Abizu Campos was considered the mastermind). The FBI operation was covert and did not become known until U.S. Congressman Luis Gutierrez had it made public via the Freedom of Information Act in the 1980s.
What act made the Abizu Campos operation secret?