PHOENIX (AP) — Government investigators are reviewing U.S. Border Patrol policies on use of lethal force amid a spate of deadly shootings along the border in recent years, including the killing last week of a teenager who agents said was throwing rocks at them from across a fence in Mexico.

Since 2010, at least 18 people have been killed by Border Patrol agents, eight in instances where federal authorities said they were being attacked by rock-throwers, a common occurrence along the Mexican border, said Vicki Gaubeca, director of the ACLU’s Regional Center for Border Rights, in Las Cruces, N.M.