According to the prosecution office, Victor Diaz Contreras was shot down by unknown attackers in his car. A woman, who was also inside the car, sustained wounds and was taken to hospital.
On Sunday, Mexico held its general election, while some regions were also voting at local elections. The country was set to elect its new president, 128 members of the Senate and 500 members of the Chamber of Deputies.
Earlier on Sunday, a female member of the Labor Party was shot dead near her house in the western state of Michoacan, the Animal Politico media outlet reported.
According to the analytical company Etellekt, 145 politicians all over the country were assassinated during the electoral campaign, as of June 30.