Mariano, a commentator for Radyo Natin-Aksyon Radyo, was fatally shot by unidentified gunmen in Laoag City, the capital of Ilocos Norte Province, according to news reports.
Mariano was riding his motorcycle home after completing a broadcast at DZJC Radyo Natin-Aksyon Radyo when assailants shot him several times in the back and head.
Local journalists believe that Mariano's death was connected to his hard-hitting commentaries. The veteran broadcaster's final program denounced illegal jueteng gambling operations in the city, as well as financial irregularities in the local electric cooperative.
A senior police officer and another suspect were charged with Mariano's murder, but a court acquitted them in 2010, saying the prosecution had failed to prove that the two were the same men who had killed the journalist.