But this gun battle kept going. As the chaos unraveled inside, police in the nation's capital shut down the surrounding area. Nearby schools went on lockdown, flights were halted at Reagan National Airport, and even after Alexis was mortally wounded by a police officer, officers chased leads that a second and possibly a third gunman had been working with him.
Twelve victims died — a body count that police say could have been much higher, even after they determined that the gunman had worked alone. Eight were injured, with all expected to survive.
More than 24 hours after the shooting, the motive remained a mystery. U.S. law enforcement officials told The Associated Press that investigators had found no manifesto or other writings suggesting a political or religious motivation.
Ron Machen, the U.S. Attorney for the District of Columbia, ticked off some of the unanswered questions Tuesday.
"What caused this individual to kill so many innocent men and women? How did he carry out and plan this attack? How did he get access to the weapons? What could have been done to prevent this tragedy? And most importantly, whether anyone else aided or assisted him either wittingly or unwittingly in this tragedy?"
Machen added, "We're not going to stop until we get answers to those questions."
Associated Press writers David Klepper in Newport, R.I., and Brett Zongker in Washington contributed to this report.