I ran into this npc for the first time the other day in an invite only session.
I'd just finished a mission for Martin and was walking out of his driveway, black sentinel barrels out of nowhere and knocks me down. I quickly jumped in my car and gave chase. As soon as I start to fire at him he slams on his brakes... gets out and proceeds to unload his uzi at me. He was a black npc wearing a leather jacket.