This story should have never made the papers.
The police should have gathered the weapons, checked for fingerprints, run the serial numbers, make them inoperable by pulling firing pins and then replaced them as they were found. Set up live video feed and snatch whoever came back to get them.
All the while, as FreedomStar3028 posted, start scouring other similar locations.
Bingo!! But it is difficult to believe the DC police got them all. So that technique is still in play. :-)
We need people like you working for the FBI, the CIA, and similar agencies (after Trump cleans house and gets rid of all the subversives there). Or maybe you could help identify and get rid of them, too.