>> reporter: one change the defense department is not considering so far is making mental health counseling an automatic disqualifier on security clearance applications, in large part to avoid stigmatizing posttraumatic stress disorder. >> i still remain in that camp, that a man or woman should have the ability with treatment to overcome them and then to have a fruitful life and gain employment, including inside of the military. >> reporter: today as co-workers were allowed back into the scene of monday's horrific shooting, aaron alexis' mother spoke publicly for the first time about her son. >> 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. >> obviously that coming from the mother. i know, jim, sort of capturing everybody to imagine what she's thinking and to imagine how the