During the Peace Walker Incident, the radioman reported to a soldier at the docks about having broken a prisoner regarding Target 500, and also was told that the "spears" were loaded onto the cargo and were prepared to be delivered, having cleared point bravo. Naked Snake, having overheard the exchange after stumbling on the beaten prisoner while infiltrating the supply facility, promptly attacked the radioman and restrained him after he hung up. Interrogating the radioman at stun rod-point, Snake learned from him that the cargo was headed to a facility within the Irazu mountain region, although Snake punched the radioman into a box filled with film badges after being distracted by the sound of Chrysalis taking off, having been programmed to find Target 500 earlier, and was then shocked by Snake by the stun rod into unconsciousness. His film badge, alongside the presence of similar film badges in the aforementioned box, were noticed by Snake shortly thereafter, with this and the radioman's earlier report causing Snake to suspect that he and the CIA were smuggling nuclear warheads into Costa Rica, and informed his lieutenant, Kazuhira Miller, as much. Because they couldn't risk either his waking up and thus alerting Peace Sentinel, or someone discovering his unconscious body, members of Snake's Militaires Sans Frontières brought him out of the facility and Fulton extracted him, after which he joined the MSF.
Behind the scenes
The radioman first appears in the Tutorial/Opening mission of Metal Gear Solid: Peace Walker, during the motion comic end cutscene. His character model during normal gameplay is that of an orange-jacketed CIA mercenary, who must be Fulton extracted in the following Extra Ops 010. The building interior where he was subdued by Naked Snake is inaccessible during gameplay, and so his unconscious body is located outside, below the balcony and near a wall.