in the 1930s, the united states-appointed governor of puerto rico, blanton winship, and the police colonel, a former u.s. army colonel named elisha francis riggs, applied harsh repressive measures against the nationalist party. in 1936, albizu campos and the leaders of the party were arrested and jailed at the "la princesa" prison in san juan, and later sent to the federal prison in atlanta. on march 21, 1937, the police opened fire on the crowd at a nationalist parade, killing 19 people in what came to be known as the ponce massacre. albizu campos returned to puerto rico on december 15, 1947, after spending ten years in prison.