Questions have swirled about the Mexican government’s response to the killing of five young men last month by members of the military. Now, human rights officials say they are investigating their deaths as executions.

Soldiers in Nuevo Laredo, Tamauplipas — across the border from Laredo, Texas — killed five young men and seriously injured another as they were reportedly driving home from a party in late February.

Human rights undersecretary Alejandro Encinas said this week that the killings didn’t result from a confrontation between the military and the victims. Instead, he says, the unarmed men were executed in their vehicle.

Officials previously announced that four soldiers had been charged with disobeying orders in the case. But Encinas says an investigation requested by the human rights commission will also look at the chain of command that could have led to the killings.