The motive for the Washington Navy Yard shooting spree that killed at least 13 people Monday remains unclear, law enforcement officials said after a chaotic day of investigating.
An alleged shooter, Aaron Alexis, a 34-year-old from Fort Worth, Texas, died in a gunfight with police and one person of interest, identified as a black man in his 50s, remained at-large, when officials last briefed the public.
"We don't know what the motive is at this stage, but we don't have any reason at this stage to suspect terrorism," said D.C. Mayor Vincent Gray. Gray said 13 people were confirmed dead and more than a dozen people were injured – though not all from gunshot wounds.
"There are probably a dozen a more who are wounded but again we're not prepared to say what all the reasons are, some may have been hurt, if I can put it that way, for reasons other than being shot," he said.
The shooting took place at Naval Sea Systems Command headquarters and began around 8:15 a.m.
Gray also cleared up questions about earlier reports of two potential suspected shooters in addition to Alexis that police were seeking.
"We don't know that there's a second shooter on the loose," he said. "We know that there's a person who was identified very early in this process, in fact there were two. One of them has been ruled out, the other person has certainly not been ruled in as someone who was involved in this horrific incident but we are trying to find him to get further information."
D.C. Police Chief Cathy Lanier said Navy Yard residents should continue to "shelter in place" as the investigation into what happens remains on-going.
"It certainly was one of the worst things we've seen in Washington, D.C," she said. "As officers entered the building and moved through the building they were making transmissions and keeping command informed as to what they were coming across as they went through – multiple victims, there was gunfire still going on. This is what we train for."
Lanier said within two to three minutes of the first call for help, police were on the scene.
"Internal security had already identified and engaged the suspect, we already had victims down at that point," she said. "Within seven minutes, we had active shooter teams inside the building, moving through the building."
The alleged gunman and law enforcement – including metropolitan and park police – engaged in multiple gunfights before the suspect was killed.
"There's no question he would have kept shooting," Lanier said.
Three victims that were brought earlier in the day to Medstar Washington Hospital Center are all doing well, according to a hospital spokeswoman.
One police officer who was shot in the leg underwent hours of surgery is expected to recover well, and another woman underwent surgery for a shoulder injury but is also expected to have a full recovery, according to Jans Orlowski, chief medical officer for the hospital. A third woman was treated for injuries to her head and her hand but will not need surgery, she said.
"She's a very, very lucky young lady – she actually has an injury to her hand and to her head but the bullet did not actually penetrate the skull," Orlowski said, adding that the hospital does not expect to treat any more injured people even as the police continue to scour Navy Yard buildings.
"It does not appear at this time, because there's been so many hours in between, it does not appear that we'll be getting any more individuals who lived through this devastating gun shooting," she said.
President Barack Obama, speaking at a previously scheduled press briefing focusing on the economy, alluded to the fact that mass killings have become an almost routine part of his presidency and offered condolences for the families affected by Monday's shooting.
"We are confronting yet another mass shooting and today it happened on a military instillation in our nation's capital," he said. "We offer our gratitude to the Navy and local law enforcement, federal authorities and the doctors who responded with skill and bravery."
Obama said he would "do everything in our power to make sure whoever carried out this cowardly act is held responsible."
The FBI has now taken over the investigation and the public will continue to get briefed as information emerges.