FORT POLK, La. — A DARPA experiment in which scientists mounted a .50-caliber machine gun on top of an iRobot Roomba 6000 vacuum cleaner did not result in the programmable sentry researchers had expected but instead achieved sentience and became the first soldier in American history to willingly police its own spent brass, defense officials said today.

A freak electric shock during a routine barracks jousting match supercharged the vacuum, according to officials, after its lance grazed unshielded wires exposed by crumbling drywall. That was when “things got weird,” said Pfc. Steve Guttenberg, who told reporters that when the smoke cleared, the Roomba immediately recited the Soldier’s Creed and pledged to bear true faith and allegiance to the cleaning of all dirt from the United States.

“We were cool with the little guy,” said Guttenberg. “Jousting is awesome, but once he started talking, I assumed a Roomba with a machine gun did the same thing as a Roomba without one.