"They gave me a medal for shooting down an enemy... and also a medal for shooting down a friend! God, I fucking love my job (of shooting things down)!"

Explanation:

tl;dr; he shot down an American transport to stop it from landing in enemy territory, where the passengers would be… not well-treated as PoWs by the Japanese Empire.

https://en.wikipedia.org/wiki/Louis_Edward_Curdes

During the attack on the airfield, La Croix was shot down and made an emergency landing in the sea. As the squadron circled, Curdes could see that his companion had survived, and remained in the area to guide a rescue plane and protect the downed pilot. While covering La Croix, Curdes noticed a larger twin-engined plane preparing to land at the Batan airfield from the east. When he saw American markings on it, he at first thought it could be a Showa/Nakajima L2D (which were Japanese license-built versions of the Douglas DC-3) with American markings. He flew to investigate and found the aircraft to be a Douglas C-47 Skytrain transport with markings of the “Jungle Skippers”, the 39th Airlift Squadron of the 317th Troop Carrier Group.[3] Curdes did not believe the aircraft to be enemy controlled and tried to make contact by radio but was not successful. He maneuvered his P-51 in front of the plane several times trying to get the C-47 to alter course, but the C-47 maintained its course.[3]

Unknown to Curdes, the C-47 had got lost in bad weather, had been flying for almost 5 hours and their radio was malfunctioning. According to an after-action report: “We received no bearings or response of any kind. The airplane continued until 1150 hours and was still over water. The pilot then informed his passengers that he was in trouble and would set the airplane down on the first land he saw.” Unknown to the pilot, the airstrip he intended to land on was Japanese-occupied.[3]

The C-47 was circling and now was attempting to land on the Batan airfield. The plane had its landing gear down and was at an altitude of about 150 feet. Curdes fired in front of the C-47, but it still maintained its course. At this point, they were close enough to shore that Japanese flak guns started firing at Curdes’ P-51, but not at the C-47 possibly because they thought it to be one of their own, especially considering Curdes’ behavior towards it.[6] Curdes reasoned that it was better to shoot down the aircraft than allow the crew to be taken prisoner by the Japanese. Curdes came about 20 yards from the C-47 and fired into one of its two engines, causing it to fail.[3] The C-47 maintained its course for Batan, so Curdes disabled the other engine, forcing the pilot to ditch in the sea. The plane successfully ditched about 300 yards from shore without breaking up and the crew was able to evacuate into lifeboats. The C-47 crew drifted to about a mile from shore and was then engaged by enemy small arms fire from the shore for about half an hour. Curdes dropped a message around this time saying: “Keep away from shore. Japs there."[3] La Croix approached and was brought on board the C-47’s life raft, where he was informed about the situation.[3]

At this point, poor light and lack of fuel forced Curdes and his wingman to return to base. Before dawn the next morning, Curdes and his wingman led the PBY-5A Catalina that picked up the downed C-47 pilot and 11 crew members, including two nurses, all of whom had survived the incident.[1] To Curdes’s surprise, he discovered that one of the nurses was a woman with whom he had to cancel a date without notice the night before shooting down the C-47. A reporter for Air Force magazine later interviewed Curdes about the incident who said: “Seven 109’s and one Macchi in North Africa, one Jap, and one Yank in the Pacific-and to top it, I have to go out and shoot down the girlfriend."[4] Curdes story was in the August 1945 issue of Air Force magazine titled, “Yank for Good Measure.” It became a rumor that Curdes married the nurse that he shot down after the war, however this is untrue. He actually met his second wife after the war in Los Angeles, California.[4] General George Kenney awarded Curdes his second Distinguished Flying Cross and an Air Medal for the event. Curdes also received credit for the “kill” and displayed it on his aircraft.[3][10][11]