Also, "US authorities had been aware of the alleged attacker, 20-year-old Wasil Farooqui, of the Roanoke area, for some time. In the past year, he traveled to Turkey and may have tried to sneak into Syria, where ISIS is recruiting and inspiring sympathizers from across the world, sources said."
Another slips through the cracks. Even with vetting, we can't stop them from SJS.