In one of the notes given to Moose, it said something about "being as serious as they were in Montgomery" or something like that. They thought at first it was Montgomery County then they decided to check other shooting crimes in the U.S. and found out that a woman was killed and one was injured in a liquor store in Montgomery, Alabama in September. The woman who survived could probably identified who shot her. Also, the credit card the killers used to have the $10 million transfered to was the one stolen from this liquor store in Montgomery, Alabama.
If it's true he was dishonorably discharged from the Army, this may be his motive for killing so close to D.C. I'm glad he and his step-son were caught. Hopefully they are the ones and the charges stick.