article_snippet: The guns were similar to the Luger pistol (pictured) that was used to murder MIT Police Officer Sean Collier .
article_snippet: Bullets for a Luger handgun were found on the Watertown street where the Tsarnaevs got in a shootout .
article_snippet: The guns were similar to the Luger pistol used to murder MIT Police Officer Sean Collier Sean Collier and engage in a shootout with Watertown police.
article_snippet: David Cahill, testified 56 bullets were fired from the Luger handgun during the confrontation in Watertown.