Two police officers have been charged with fatally shooting a U.S. citizen and a U.S. legal resident at a highway checkpoint near Saltillo in the northern border state of Coahuila, prosecutors said Monday.

Police apparently tried to cover up the killings with a now-discredited story that the Americans fired at officers first.

The two officers of the elite, SWAT-style GROM police squad were manning a highway checkpoint near Saltillo on Oct. 28, when the two men later identified as the Americans allegedly failed to stop at the checkpoint.

A statement issued by police later that day claimed the officers "gunned down two armed civilians after they (officers) responded to an armed attack."

The police account said the two men were speeding and tried to avoid the checkpoint. "Several yards down the road they fired their weapons several times at the GROM officers, who chased them," the statement said. It said that "the officers returned fire, killing the two suspects."

An official in the state prosecutors' office said contradictions in that version led investigators to test the Americans' hands for gunpowder residue and none was found. The official said the two men were simply driving through Coahuila on a highway that heads south. Rules of the prosecutors' office do not allow the official to be quoted by name.

The two police officers are in jail awaiting arraignment on first-degree homicide charges.

The official identified the U.S. resident as Edgar Valdes Rodriguez of Kansas City, Missouri. The U.S. State Department identified the dead U.S. citizen as Demetrius Atkins, giving no hometown.

The case recalls a 2010 killing of another American at a checkpoint in Mexico, where police and soldiers have a reputation for sometimes tending to shoot first and ask questions later.

In August 2010, soldiers killed Joseph Proctor, a 32-year-old New York native, at a roadblock near his home north of Acapulco.

The military said the construction worker tried to attack the soldiers with an AR-15 rifle. His family fought the claim and pressed for an investigation. Weeks later, the Mexican Defense Department released a report to his mother, Donna Proctor, saying three soldiers were charged in the death.