Luis Lima, 68, died in his vehicle in front of the radio station in Zacapa department, about 270 kilometres (165 miles) east of the capital Guatemala City, a spokesman for the fire service told local media.
Lima, who hosted a program called "We are Zacapa," is the third journalist killed, early yesterday in the central American country so far this year.
Guatemala has been struggling with a wave of violence, related mainly to drug trafficking, that has seen an average of 16 people killed a day.