Pentagon Turns to Review for Navy Yard Answers

Defense Secretary Chuck Hagel says study of security will reveal how Aaron Alexis kept his clearance.

Secretary of Defense Chuck Hagel and Joint Chiefs Chairman Gen. Martin Dempsey brief the press at the Pentagon on Monday, Sept. 18, 2013, in Arlington, Va.

Defense Secretary Chuck Hagel and Joint Chiefs Chairman Gen. Martin Dempsey authorized a review of physical security and access at the hundreds of Department of Defense facilities worldwide in response to the Navy Yard shooting.

By + More

Top Pentagon officials are leaning heavily on an upcoming review to explain why a contract employee with a history of mental instability and firearms citations was able to enter the Navy Yard on Monday and kill 12 of his co-workers.

[READ: Alexis Used Shotgun, Handgun in Navy Yard Shooting, Authorities Say]

Defense Secretary Chuck Hagel on Wednesday confirmed earlier reports that he has authorized a review to study physical security and access at the hundreds of Department of Defense facilities worldwide. It will also review the process by which DoD employees are issued security clearances, and how often they are reviewed.

While speaking at a press conference on Wednesday with Joint Chiefs Chairman Army Gen. Martin Dempsey, Hagel deferred all questions on the troubling history of alleged shooter Aaron Alexis to the aftermath of this review.

"We don't live in a risk-free society. Every day all the millions of DoD employees, uniform or civilian, come to work," he said. "There's always some risk to that. And that isn't a good answer. That's not good enough."

"We will find those gaps and we will fix those gaps. To go beyond that...I would leave that to the review. There are many questions that are going to be asked,' he said.

There are more than 300 active duty military installations worldwide, according to the Pentagon's latest "Base Structure Report" to Congress, and 523 total facilities. This excludes temporary facilities, such as forward operating bases in Afghanistan.

[PHOTOS: At Least a Dozen Killed in Washington Navy Yard Shooting]

Alexis reportedly called police in August of this year to complain of voices harassing him in his Rhode Island hotel room . Local police alerted nearby Newport Naval Station about the contractor's claims.

He also had a history of run-ins with police over shooting incidents in Forth Worth, Texas and in Seattle.

Hagel said his review, to be led by Deputy Defense Secretary Ash Carter, would determine how Alexis was able to retain his secret clearance as a contractor at the Navy Yard despite this disturbing trail.

There have been at least 20 mass shootings during the Obama presidency, many of which have targeted military personnel. Maj. Nidal Hassan was sentenced to death in August for the 2009 shooting at Fort Hood, Texas that killed 13 and wounded more than 30.

A string of high-profile leaks have also called into question the access given to Defense and intelligence employees, such as former NSA contractor Edward Snowden or former Army intelligence analyst Chelsea Manning.

Gen. Dempsey said Wednesday that this alarming string of events prevented Monday's attack from even more bloodshed

"Early indications are [these events] actually contributed to a less horrific outcome: More alert notices, coordination in advance of crises with other agencies of government, training for employees and law enforcement on active shooter scenarios," he said. "We believed it reaped the benefit it intended."

[ALSO: Preventing Another Navy Yard Massacre Begins at Work, Experts Say]

Dempsey also reinforced his support of eliminating questions of previous mental difficulties on some security clearance forms.

"I was one of those..who believe that men and women should have the opportunity to overcome their mental disorders or their mental challenges, or their clinical health challenges and shouldn't be stigmatized," he said. "I remain in that camp, that a man or woman should have the chance to, with treatment, to overcome them and have a fruitful life and gain employment, including inside the military."

Alexis committed murder, the general said, adding he didn't believe a question or lack of a question on a security clearance form would have revealed his intention to do that.

More News: