Isabelo Rivera Negrón was the 21st Puerto Rico Adjutant General, and the commanding officer of the Puerto Rico National Guard.

The Puerto Rico National Guard (PRNG) –Spanish: Guardia Nacional de Puerto Rico– is the national guard of the U.S. Commonwealth of Puerto Rico. The Constitution of the United States specifically charges the National Guard with dual federal and state missions, which includes to provide soldiers and airmen to the United States Army and U.S. Air Force in national emergencies or when requested by the president of the United States, and to perform military operations at the state level or any other lawful service as requested by the governor of Puerto Rico. The PRNG responds to the governor of Puerto Rico, who serves as its commander in chief and imparts orders with the Puerto Rico adjutant general acting as conduit, and its local mission is to respond as requested in military or civilian tasks. Abroad, its main function is to train a reserve capable of providing additional personnel in a war scenario.