The deadly shooting at one of the region's largest military facilities Monday reopened the debate about whether officials have done enough to secure the nation's massive portfolio of domestic bases.
At least 13 people were killed and several more were wounded, authorities said, when a 34-year-old Texas man and former Navy reservist allegedly opened fire from inside the Washington Navy Yard in one of the most violent such incidents ever on a U.S. military installation.
National security analysts say the Pentagon has improved security at its posts following the 2001 terrorist attacks and, more recently, the 2009 shootings at Fort Hood, Texas. In that case, a radicalized Army psychiatrist shot 13 people to death and wounded more than 30 others.
But the analysts say more could be done to screen military personnel for mental health problems — though it's not clear that such action would have prevented Monday's rampage.
"Given the task at hand, they've done remarkably well," Jeffrey Addicott, director of the Center for Terrorism Law at St. Mary's University in Texas. "If you think about the thousands of people who go on to military bases, it's impossible stop and search every car."
But Addicott said Pentagon officials also need to improve their advance screening of military personnel for signs that they could become violent.
"If you're trying to stop them at the gate, you're too late," he said. "We need to have better screening processes."
Authorities are well aware of the challenge. Just last month, Navy Secretary Ray Mabus ordered the creation of a program to counter "insider threats."
The program, which calls for better training and increased scrutiny of Navy and Marine Corps personnel, is aimed at thwarting not only violent attacks, but also security breaches such as those carried out by Army Pfc. Bradley Manning and National Security Agency contractor Edward Snowden.
Improved mental health screenings was among the top recommendations of an independent panel commissioned by the Defense Department to review the Fort Hood shooting.
Former Maj. Nidal Hasan, an Army psychiatrist who had worked at Walter Reed Army Medical Center in Washington, was sentenced to death last month after admitting to the killings.
The review panel also called for better background checks on civilians who enter military installations and foreign nationals who work for the Department of Defense.
Until Monday, the Fort Hood massacre was the deadliest mass killing on a U.S. military installation — but it was not an isolated case.
Six months earlier, a self-described Islamic radical shot and killed an Army private at a recruiting center in Little Rock, Ark. In March of this year, a Marine killed two officer candidates before killing himself in Quantico, Va.
At a congressional hearing in late 2011, Pentagon officials told lawmakers they had found at least 33 public cases since the 2001 attacks in which "homegrown terrorists" had attacked military installations or planned to do so. An assistant defense secretary, Paul Stockton, told lawmakers at the time that the Pentagon was dealing with the threat.
"Let me provide you with my bottom line up front: The terrorist threat to our military communities is serious, and will remain so for years to come," Stockton said.
Authorities said Monday they are investigating a motive for the shooter, whom they identified as Aaron Alexis of Fort Worth.
Mabus told CNN that Alexis, who was also killed Monday, was a civilian contractor. Records released by the Navy show the New York City native served in the Navy from 2007 to 2011, and worked as an aviation electrician's mate 3rd class at Fleet Logistics Support Squadron 46 in Fort Worth.
The Washington Navy Yard, the nation's oldest military facility, is the central feature of a rapidly developing neighborhood along the Anacostia River in Southeast D.C. More than 15,000 service members and civilians work at the facility.
The Department of Defense counts more than 440,000 buildings in its domestic portfolio located at about 4,400 sites. Generally, visitors are required to show a military ID to enter a base or they are escorted. Vehicle inspections are common.