[2021] TD2 - Encountering real players in their campaign

I apologize if this is an obvious stupid question, but cant seem to see reference to my question. I am still relatively new to Div2, a couple months in & really enjoying many aspects. I recently finished the main storyline & WONY & noticed from time to time, most often when leaving a safe house, I have come across other players in my world. At first I thought they were rogue agents, but I see actual names & ranks & I was not in the dark zone. They looked as confused as me, , I did not request an agents help, & did not respond to the request. In fact it had always ended with them shooting at me. I thought maybe I am overlooking a PVP aspect, but cant find anything. Is this a glitch? or some aspect of pvp I have been missing?