Sergeant Lounge was carrying his AR15 and a ballistic shield from his cruiser.

WHITEHOUSE: Background on Medal of Valor Ceremony

The United States and NATO have begun to field an anti-ballistic missile shield in the southern and eastern parts of Europe to protect from such a threat.

CNN: STORY HIGHLIGHTS

During his time in office, the United States has moved steadily toward the deployment of a shield against ballistic missile attack.

CENTERFORSECURITYPOLICY: Testing, testing

The Russian Defense Ministry maintains that the U.S. missile shield program would violate the 1972 Anti-Ballistic Missile treaty signed by Russia and the United States.

CNN: US - After test fails, Russia again urges U.S. to drop missile shield proposal

Moscow has long opposed American plans to build a so-called defence shield in and around Europe capable of shooting down ballistic missiles.

BBC: Obama and Medvedev caught in unguarded missile remarks

Critics believe the missile shield would spell an end to the 1972 Anti-Ballistic Missile (ABM) treaty, and some European leaders agree with Russian warnings that it could start a new arms race.

CNN: UK signals support for missile plan