Pantin's Socialist Party. Barceló and Muñoz Marín were both elected Senators. By 1936, differences between Muñoz Marín and Barceló began to surface, as well as between those followers who considered Muñoz Marín the true leader and those who considered Barceló as their leader. Muñoz Marín and his followers, who included Felisa Rincón de Gautier and Ernesto Ramos Antonini, held an assembly in the town of Arecibo to found the Partido Liberal, Neto, Auténtico y Completo (Clear, Authentic and Complete Liberal Party), later named the People's Democratic Party (PPD for Spanish name). During the 1930s and 1940s, Nationalist partisans took part in violent incidents: On April 6, 1932, Nationalist partisans marched into the Capitol building in San Juan to protest the legislative proposal to approve the present Puerto Rican flag, the official flag of the insular government. Nationalists preferred the flag used during the Grito de Lares. On October 24, 1935, a confrontation with police at University of Puerto Rico, Río Piedras campus, killed four Puerto Rican Nationalist Party supporters and one policeman. The event came to be known as the Río Piedras massacre. On February 23, 1936, Colonel Elisha Francis Riggs, formerly of the US Army and the highest police officer in the island, was assassinated in retaliation for the Río Piedras events by Nationalists Hiram Rosado and Elías Beauchamp. Rosado and Beauchamp were arrested, and summarily executed without a trial at the police headquarters in San Juan. On March 21, 1937, a march in Ponce by the Puerto Rican Nationalist Party, organized to commemorate the ending of slavery in Puerto Rico, resulted in the deaths of 17 unarmed citizens and 2 policemen at the hands of the territorial police, an event known as the Ponce massacre. In 1936, the U.S. Senator Millard Tydings presented a legislative proposal to grant independence to Puerto Rico, but many people believed that it had unfavorable economic conditions. Barceló and the Liberal Party favored the Bill, because it would give Puerto Rico its independence; Muñoz Marín opposed the Bill because he wanted Puerto Rico's immediate independence but with favorable conditions. On July 25, 1938, shots were fired at the US colonial governor, Blanton Winship during a parade; they killed Police Colonel Luis Irizarry. Soon afterward, two Nationalist partisans attempted to assassinate Robert Cooper, judge of the Federal Court in Puerto Rico. Winship tried to suppress the Nationalists. On June 10, 1948, the United States-appointed