[5] A direct participant in the most risky actions of the FPMR, in September 1986, he won the trust of Raúl Pellegrin's leadership by organizing one of the four groups of riflemen in the assassination attempt against Augusto Pinochet.

Mauricio Hernández is often credited as the intellectual leader of the murder of Senator Jaime Guzmán, carried out in 1991, which was a time where the FPMR was arguing between either continuing armed operations or tactical withdrawal.

On 5 August 1993, he was arrested by the Investigations Police of Chile at a gas station in Curanilahue along with his bodyguard, Agdalín Valenzuela, who would be executed two years later by his fellow FPMR militants after being accused of having turned him in.

He was also convicted of infraction of the arms law, illicit association, terrorist conduct, falsification of public instruments and impersonation.

He also recognized his actions in the kidnapping of Carlos Carreño (colonel of the army) and Cristián Edwards (son of the owner of the pro-Pinochet Chilean newspaper El Mercurio), in an explosive attack at the National Stadium and in countless bank robberies.

On February 2, 2002, Mauricio Hernández was arrested along with six other people in the town of Serra Negra after accused of the kidnapping and subsequent captivity of the Brazilian businessman Washington Olivetto in 2001.

[17] The chilean punk rock band Curasbun wrote a song about him in their 2016 album Inmortales (Immortals), simply titled "Ramiro".