The Division, like most games released recently, has had a rough startup.
YouTuber Extended Celery has shown off a bug that pretty much ruins PvP on Reddit. A technique performed by throwing a seeker mind and pulling out the shield, you can then swap between your primary pistols rather then being limited to your pistol.
As he points out in his video you could use a sniper from a very far distance and just pick people off while hiding behind a shield. There doesn’t appear to be a way to get around this bug, so if you see someone doing using it, it’s best just to run the other way.
Others have started coming forward listing other ways of doing it. After reviving a team mate, and doing a fakey turret run, it can happen. The bug has been reported on the official forums.