Everything is clear - he tricked her into sex, but who really filmed it? He obviously filmed it with a different camera than the one he had in his hands! A hidden camera does not give this angle and quality of shooting! So the cameraman in the room with a professional camera and a camera in his hands just a farce.
Didn't want to get caught, I'd close the doors when masturbating. If you left them open, be good enough to serve your brother. That's the logic!