At least 12 people, including Indian-American defense contractor Vishnu Pandit, were killed by a lone gunman who was shot down after the brazen shooting rampage at the high-security Navy Yard on Monday.
"Obviously, there were a lot of red flags. Why they didn't get picked, why they didn't get incorporated into the clearance process, what he was doing, those are all legitimate questions that we're going to be dealing with. How do we fix it?" Hagel said at a news conference.
Hagel has also ordered security reviews to be carried out by Deputy Secretary of Defense Ashton Carter, who is currently in India.
"Yesterday, I directed two department-wide reviews. These reviews will be led by Deputy Secretary Ash Carter, and we will do everything possible to prevent this from happening again," Hagel said.
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"Second, Deputy Secretary Carter will also lead a review of DOD's practices and procedures for granting and renewing security clearances, including those held by contractors. This review will be closely coordinated with other federal agencies, including the Director of National Intelligence and Office of Management and Budget, currently examining these procedures," he said.
"I've also directed that an independent panel be established. This independent panel will conduct its own assessment of security at DOD facilities and our security clearance procedures and practices. The panel's work will strengthen Secretary Carter's efforts, and they will provide their findings directly to me," Hagel said.