It is unlikely that you could use a big strapping white man for a spy in Pakistan. It is like a Polar Bear walking the streets of NY. He had a specific job assignment and it wasn’t covert.
That is what happened. Our guy had no idea the two guys he shot were ISI agents shadowing him. The situation screamed ambush and he reacted like he was trained. Given the ISI, he might have been right too, not that the ISI would admit it.