Gunmen lined up six young men and killed them in a neighborhood in Monterrey, the capital of the northern Mexican state of Nuevo Leon, officials said.

“A group of armed men arrived in a taxi and an SUV in one of this city’s neighborhoods and killed them like a firing squad with large-caliber weapons in front of a house,” a state Security Council spokesman told Efe.

The gunmen caught the victims by surprise Wednesday at the intersection of Planicie and Los Rodriguez streets, the state Security Council spokesman said.

Investigators gathered up numerous bullet casings from AK-47 assault rifles at the crime scene.

The victims were known drug dealers in the neighborhood, residents said.