Marco Aurelio Ramirez, 69, was killed in broad daylight as he left his home in the town of Tehuacan. He had worked for decades for several different media outlets, according to Barron's
An investigation into the crime was opened, the prosecutor's office said.
The Mexican branch of Reporters Without Borders (RSF) said that Ramirez, working as a civil servant, had contributed to the arrest of suspected criminals.
"RSF calls for a swift and transparent investigation," the non-governmental media rights group said, to determine "whether the homicide was related to his work as a municipal official or to his practice of journalism."
More than 150 journalists have been killed in Mexico since 2000, according to RSF. Most of the murders have gone unpunished.
This was the third journalist to be killed in the country this year.
SKH/PR