(NBC News) Two days after the deadliest attack on a military installation in years, questions are mounting about security lapses at the Washington Navy Yard and why the shooter was granted clearance.
Shaken employees are still trying to grasp the tragedy that unfolded Monday.
Those allowed to return to the Navy Yard Wednesday morning gathered their belongings.
Many lost friends, 12 men and women, all civilian contractors.
Meanwhile, the gunman's mother spoke out for the first time.
Cathleen Alexis, not appearing on camera, said "I don't know why he did what he did, and I'll never be able to ask him why. Aaron is now in a place where he can no longer do harm to anyone, and for that I am glad. To the families of the victims, I am so, so very sorry that this has happened. My heart is broken."
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