GracefullyIgnorant t1_jcr9c4u wrote

It was very common for fighters to have gun cameras to confirm kills. Usually they'd start recording when the guns fired, but in some instances the pilots could activate them whenever. Otherwise there would be confirmation of a kill from a wingman, an observer on the ground, or even sometimes the enemy. In this instance, I'm sure there would be physical evidence as well, such as bits of Japanese plane stuck in the engine cowling!