Became an active participant in radio dramas at the Manila Broadcasting Company (MBC) and DZRH at the age of 17. Studied chemical engineering at college, but was not able to get a degree due his engagement with the entertainment industry. Started his film career collaborating with the late Lino Brocka; they first met at the MNC in 1968. Insiang (1976), directed by Lino Brocka, was the first Filipino film to screen at Cannes; the movie story and screenplay were written by Mario. Joined the Philippine Educational Theater Association (PETA) in 1969. Made his directorial debut with the film Mortal (1975). Awarded many times throughout his career, the most notable being the Best Screenplay award for Rubia Servios (1978), the Best Director award for Bulaklak sa City Jail (1984) and the Best Director and Best Actor awards for Halimaw (1986) at the Metro Manila Film Festival. Wrote the musical called Stageshow, one of the official entries to the National Theater Festival held in 2012. Died of acute leukemia.