Probably he claimed on 200 that you had picked him, too.
Happens to me all the time. Just two days ago: Come a cross a lone P-39 in an otherwise empty sector in my 109G-6. I dive upon him, he spots me in time, avoids me. We race down to the deck, he dies (I think he'd blacked out).
Of course he came on 200 saying I'd picked him.
I really don't get why people are doing this unprovoked.