Ramón Chávez Ávila, a former alderman in the municipality of Tepecoacuilco, northern Guerrero, was killed in the morning just a few steps from the mayor's office, according to reports.
The death of the member of the leftist Democratic Revolution Party (PRD) was reported by an anonymous caller, who said that he was killed in a shootout, according to the authorities.
He was a candidate for mayor a decade ago.
Chávez Ávila was found dead inside his construction material business, just next to the mayoral office, with two bullet wounds in the head.
The 55-year-old Chávez Ávila was a local leader of the PRD and worked as an alderman from 2002 to 2005.
Tepecoacuilco, along Iguala and Cocula, is in the northern areas of Guerrero, which has seen an increase in violence and homicides according to data from the Ministry of the Interior.