Aaron Alexis, whom the FBI believes to have been responsible for the shootings at the Washington Navy Yard in Washington, D.C., is shown in this handout photo released by the FBI on Monday.
September 19, 2013 USIS, which processes thousands of background checks a year for the U.S., is being investigated for "systemic failure" to adequately vet employees and contractors. The company would not comment on the specifics of the Alexis investigation.
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