Mr300: I believe that is the Bizon 9mm submachine gun. It is AK based but uses a helical magazine like our Calico models except it extends forward under the barrel.
if you look closely it appears he is using the hammer drop. He does not even have his finger on the trigger when it goes forward. I think he racked the slide and handed it to Ivan. It looks like in the last moment before he pulls the trigger he attempted to slap it out of his hands most likely realizing he racked it with a round now in the chamber.