Mr. Pride chose to shoot, firing a single shot that killed Officer Peter Figoski in the early morning hours of Dec. 12, 2011, prosecutor Kenneth Taub told a jury on the first day of a joint murder trial against Mr. Pride and Michael Valez, the alleged getaway driver that night.

WSJ: Trial Opens in Slaying of Officer

In one famous raid in late 2003, Petraeus' forces arrested some three dozen insurgents firing just a single shot.

NPR: White House Shuffles Its Leaders on Iraq, Security

Earlier this week Wilson posted a video online showing a single shot being fired from "The Liberator, " a plastic handgun that, with the exception of a metal firing pin and a piece of metal included to comply with the Undetectable Firearms Act, was assembled entirely from parts made with a 3-D printer.

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