The local public safety secretary says Matehuala Mayor-elect Edgar Morales Perez and aide Francisco Hernandez Colunga were returning from a birthday party when they were ambushed early Sunday in the town. Hernandez Colunga's wife was also in the car but survived the attack. The assailants remain at large.
Morales Perez had belonged to the Institutional Revolutionary Party, which regained the country's presidency last month. He was scheduled to take office in September. The National Action Party had governed Matehuala for years before his electoral win.
A car filled with 14 corpses was found Thursday by a gas station along a highway in San Luis Potosi state.