An unidentified Mexican man has been shot and killed by a Border Patrol agent in the United States just over the frontier near Naco, authorities said Sunday.

The Cochise County Sheriffs Office and the Border Patrol's Tucson Sector headquarters said the shooting took place Friday. Lt. Commander Mark Dannels of the Sheriffs Office said the confrontation began as a rock-throwing incident.

"The officer was in fear of his life and took the actions he deemed appropriate," Dannels said.

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In Mexico, the Foreign Relations Department condemned the shooting on Saturday, which it said was about 550 yards north of the Mexico border.

"The department expresses its profound concern over this kind of disproportionate violence that results in the loss of human lives," the department said in a news release. "Above all, when force is used against people who do not represent a threat to United States authorities."

The department did not identify the man except to say he was 22 and from the Mexican central state of Puebla. It said the shooting occurred when he was detained along with several others, including three relatives, by Border Patrol agents in Naco, Ariz.

An investigation into the incident is ongoing. The Border Patrol agent involved in the shooting has been placed on paid administrative leave pending the outcome of the investigation, Rodriguez said.

Meanwhile, the Foreign Relations Department has instructed its diplomats in Arizona and Washington to launch their own investigations.

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