7:53 p.m. ET -- The wounded Washington police officer who was in surgery today at Medstar Washington Hospital Center was shot multiple times in the legs, and doctors will begin to determine on Tuesday whether he will be able to keep the legs, CNN's Chris Lawrence reported.
7:42 p.m. ET -- The names of those killed won't be released until 24 hours after the last relative on the entire list is notified of the deaths, a Pentagon official told CNN's Barbara Starr. This is the same way the Defense Department treats a mass casualty incident in a warzone.
7:11 p.m. ET -- Before the shooting, Alexis drove into the naval yard with his military contractor identification card, a U.S. law enforcement official told CNN's Evan Perez.
Alexis, armed with three guns, walked into Building 197, made his way to an overlook above an atrium, and started shooting, the official said.
6:54 p.m. ET -- Multiple law enforcement sources say that only one weapon was recovered from the scene of the shooting, CNN's Evan Perez and Pamela Brown report. The sources say the weapon was a "long gun."
6:47 p.m. ET -- Michael Ritrovato, a friend and former roommate of Alexis, told CNN that Alexis was frustrated with the company that contracted him to work for the Navy.
Alexis claimed he wasn't paid properly by the company after returning from a months-long assignment to Japan last year, Ritrovato said.
It was unclear whether the dispute was over salary or expenses. Alexis just felt the company owed him money and had not paid him, Ritrovato said.
6:44 p.m. ET -- One of Alexis' friends, Nutpisit Suthamtewakul, told CNN's Ed Lavandera that he had been Alexis' roommate for three years near Fort Worth, Texas, ending a few months ago when Suthamtewakul got married.
Alexis befriended Suthamtewakul four years ago after he emigrated from Thailand, and taught Suthamtewakul about American culture, Suthamtewakul told CNN. Alexis, he said, was fluent in Thai and attended a Buddhist temple.
When Suthamtewakul opened the Happy Bowl Thai Restaurant, Alexis would occasionally help out, waiting tables, he said.
Suthamtewakul reeled at the news that Alexis was believed to be a gunman in the rampage at the Navy Yard.
"I can't believe he did this," he said. "He never showed any sign of violence."
6:20 p.m. ET -- Alexis was discharged from the Navy following a "pattern of misconduct," a U.S. defense official told CNN's Barbara Starr. We previously reported that he left the Navy in January 2011.
6:15 p.m. ET -- Investigators still don't know of a motive in the shooting, D.C. Mayor Vincent Gray said at a news conference moments ago.
And investigators still are looking for a person who, other than Alexis, might have been involved in the shootings, Gray said. Like before, the description of this person is: a black man in military-style drab-olive clothing, about 50 years old, and about 5 feet 10 inches tall, with gray sideburns.
Washington Police Chief Cathy Lanier said that one of the three wounded people being treated at MedStar Washington Hospital Center -- a Washington police officer -- is out of surgery and is in a stable condition.
"We know he's going to be OK," Lanier said. The other two patients also are expected to survive, a hospital official told reporters earlier.
6:02 p.m. ET -- When asked whether Alexis was authorized to be at the Navy Yard, Secretary of the Navy Ray Mabus said that was "part of the investigation."
"The only thing we know was that at one point, he was a Navy contractor. Whether he was today, I don't know," Mabus told CNN's Wolf Blitzer.
5:56 p.m. ET -- Alexis was most recently a Navy contractor working in the area of information technology, Secretary of the Navy Ray Mabus said.
We previously noted that Alexis left the Navy in January 2011 as an aviation electrician's mate 3rd class, after a nearly four-year Navy career. Mabus said that Alexis worked on airplane electrical systems.
5:25 p.m. ET -- Navy Capt. Mark Vandroff says he was in the middle of a meeting on the third floor of the yard's Building 197 on Monday morning when he heard someone shouting about gunshots being fired there.
"Lock the doors! Lock the doors," the person shouted, according to Vandroff.
He and others took shelter in a conference room and in other rooms, and they lay on the floor for about an hour and a half, occasionally texting colleagues to get information about their situations. Over the course of about 40 minutes, gunshots could be heard intermittently, he said.