If I had been the store owner in this case, I would have delayed selling him the armor with an excuse, (too small, too large) AND asked him for a contact number and address to contact him if the right size was available. At least that idea came to mind when I read about the store event.
Most stores have video. The shooter was very security concious. I wonder if he scoped the store out for cameras before he asked about the body armor and ammunition.
If the FBI were really intent in these cases, they could have asked for phone information from nearby towers to find out who was calling at the time he was in the store.
yeah I would also given him a 10% off business card if he left his info..so they could call him when it came in or some such
also followed him to parking lot and gotten vehicle info make model color plates... hindsight isgreat isnt it..they also should have kept the part od the video with him on it put it on a thumb driveor saved it ...