Gunmen kill the mayor of a small Mexican town and 3 others in a highway attack

Authorities say gunmen have killed the mayor of a small Mexican town along with three other people in a highway attack on their vehicle. The federal public safety department said the killings occurred late Sunday in the northern state of San Luis Potosi. Authorities said the possible motive in the attack was under investigation. The attack was the latest in a series of killings of public officials in Mexico. The motives for killings of mayors in Mexico have included political differences, conflicts over corruption and drug cartel pressure on local officials.