More details have been released about exactly how law enforcement officers tracked down and killed the Navy Yard shooter.
At the scene of the shooting, a U.S. Park Police patrol officer and a D.C. Police officer got together to form what's called an "active shooter team." Each officer was armed with a rifle, says Park Police Union chairman Ian Glick.
"They went in, addressed the threat, and neutralized him," he says.
He says inside Building 197, the two had to navigate a maze of office cubicles.