Defender Rockfowl

At the Fairfax ruins- the stop light intersection, the defender is very likely to step over a mine and kill himself as he fights some other NPC raider. You must hurry to him before he kills himself if you want to interact with this guy later in the game. I don't know that interacting with him later on in the game anything more than dialog speech.

He carries a minigun some amo and a pass to enter an outcast base?

He seems to spawn at the stop light after you engage one of the near by raiders.