Guns don’t kill people, shooters kill people

It was dark, there were noises and then gunfire:

Friendly fire probably killed a U.S. Border Patrol agent in Arizona near the Mexican border this week, the FBI said on Friday … a "tragic accident, the result of friendly fire."
— David Schwartz, “Probe points to friendly fire in Arizona Border Patrol death”, Reuters, 6 October 2012

In the dark, it seems as if an agent heard a noise, saw a shadow, and other agents thought they were being fired on by an assailant – and agents shoot to kill when under attack. Border Patrol agents are intensively trained in the use of guns, and they are experts.