Ahh ,caught me out there… I should have worded it a bit different to be fair, shouldn’t I?!
This is where I got my info from, the NASM Smithsonian web site,

P-61s arrived in the Pacific Theater at about the same time as the European Black Widows. For years, the Japanese had operated lone bombers over Allied targets at night and no U. S. fighters could locate and attack them. However, on June 30, 1944, a Mitsubishi BETTY (see NASM collection) became the first P-61 kill in the Pacific. Soon, Black Widows controlled the night skies. On the night of August 14-15, a P-61 named “Lady in the Dark” by her crew encountered an intruding Nakajima Ki-43 Hayabusa (Peregrine Falcon) OSCAR (see NASM collection) and eventually forced it into the sea without firing a shot. Although the war was officially over, no one was sure that all of the Japanese had heard the message and stopped fighting. The American night fighters flew again the next night and “Lady in the Dark” again found a target. It was a Nakajima Ki-44 Shoki (Demon) TOJO and the fighters maneuvered wildly as they attempted to gain an advantage. The P-61 crew lost and reacquired the Ki-44 several times then finally lost it for good and returned to base. The next day ground troops found the wrecked TOJO. In the darkness, Lady in the Dark’s crew had forced the Japanese pilot to fly into the ground, again without firing a shot.

I guess I should have said ‘credited with the last air to air kill’, rather than shot down!

Interesting question though.
Cheers, Alan.