Law enforcement officials have labeled him a terrorist since the 1970s.
López Rivera, who was serving more than 50 years in prison for plotting to overthrow the US government, belonged to Armed Forces of National Liberation, known by its Spanish acronym FALN. The group often fought for Puerto Rican independence through violence and was connel
In 1981, López Rivera was sentenced to 55 years in prison for "seditious conspiracy" and other felonies. He was later sentenced to an additional 15 years in 1988 for conspiracy to escape; to transport explosives with intent to kill and injure people; and to destroy government buildings and property.
López Rivera wasn't charged directly in FALN's attacks but more broadly with charges of plotting to overthrow the US government.
FALN first announced itself in 1974, when it took credit for five bombings in New York.
The group was responsible for dozens of bombings and incendiary attacks during the decade, according to law enforcement officials. The bombings were called terror attacks and resulted in at least five deaths and more than $3 million in property damage, according to a 1999 House report for the Committee on Government Reform.
In one attack for which the group claimed responsibility, a booby-trapped body was used to lure a NYPD officer into an abandoned building. The resultant explosion permanently disabled the officer.
In late 1976, Chicago police uncovered a bomb factory run by FALN, a discovery that led to the arrest of López Rivera, the House report said.