Weird Atomic Bug

I was playing Bullet Atomic Chess against someone, and I made the checkmating move, but instead of it saying "Checkmate", it ran his time down to zero (not a big deal since it was 1/4+1). Any idea what happened here? lichess.org/OScM71LJ#34

Oh wait nevermind I see now that he had en passant =/. Sorry for creating this extraneous thread.