Government investigators are reviewing the U.S. Border Patrol's lethal force policies amid a spate of deadly shootings, including last week's killing of a teenager who agents said was throwing rocks from Mexico.
The Department of Homeland Security's Office of Inspector General probe involves a review of accusations of excessive force.
Vicki Gaubeca, director of the ACLU's Regional Center for Border Rights, says at least 18 people have been killed since 2010 by agents, eight where authorities said they were being attacked by rocks.
The review came after members of Congress sought a probe into the 2010 San Diego death of an unarmed Mexican migrant. They asked authorities to determine whether the incident is part of a broader cultural problem within the agency.
The Border Patrol says it cooperates with all investigations.