(NEWSER) – A US Border Patrol agent who claims he feared for his life after a rock hit his head reacted by shooting and killing the man who hurled the stone. It marks the ninth fatal shooting involving rock throwing since 2010. The unnamed agent was patrolling a smuggling trail east of San Diego early Tuesday when he came upon men suspected of crossing the border illegally; rocks were thrown at him, with one hitting his head.

The San Diego Union-Tribune describes one of them as being as large as a basketball, and many of the rest fist-sized. The APreports that the incident fuels an ongoing debate over whether lethal force is justified as a response to rock attacks. The Border Patrol has long maintained that rocks are deadly weapons, and has rejected proposals that would prevent it from responding to them with deadly force.

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