I tied Alex to the chair and made him cum

After a few first minutes of this video, his head is not visible, and he is not moving anymore. He even cummed in silence. Can't say what I did to him behind the scenes. Why is he like that? Why is he still hard and even cummed, but doesn't moan and doesn't move? Shady clip of ambiguous nature, but let's say it's basically a handjob given to a tied twink. Closeups and cum play included.