Keegan was working with the Ghosts to clear an area of enemy soldiers. The building was large, so they split up, constant radio check-ins.

When he entered a room, he kept his gun trained ahead of him. Before he could check the corners, someone fought with him, knocking his gun away from him and forcing him onto the ground.

He was able to scramble back to try and recollect himself, but the enemy already had their sidearm aimed at him. That's when he saw it, the birthmark on their right cheek.