However, further verification is required as there are a theory of his having committed suicide with a gun (Koshu OGASAWARA and Jiro NITTA, who interviewed him, put forward this theory) and another theory, by Akitomo MATSUKI, that needs more background says, 'It was impossible for his frozen fingers to manipulate a gun.'
しかしピストル自殺説（小笠原孤酒及び彼に取材した新田次郎が採っている）もあることや「凍傷の指で銃の操作は不可能」として新たな背景を探る松木明知の研究もあり、更なる検証・進展が望まれる。