An official in Cuautitlan Izcalli, a city in central Mexico, was murdered while taking part in a clean-up event, municipal officials said.
Zoe Zambrano, who served as director of the city water company, was shot in the head and killed on Saturday.
Zambrano was murdered "while participating in a city-sponsored cleaning day," officials said.
Cuautitlan Izcalli is in Mexico state, which surrounds the Federal District and forms part of the Mexico City metropolitan area.
Zambrano and several other people were cleaning in the streets when a gunman got out of a vehicle, walked up to the city official and fired, media reports said.
The gunman returned to the vehicle and drove away with an accomplice.
Investigators are gathering evidence and plan to meet with the official's family and friends to try and come up with a lead in the killing, the Mexico state Attorney General's Office told EFE.