Ground ball to 3B.
First basemen is a lefty. But instead of catching the throw with his left foot on the bag and his right arm and hand extended away from the bag, he catches the ball in a manner where his mitt is directly in the path of the batter/runner coming to first base. There is a collision with the runner and the 1B mitt and the mitt (with the ball still in it) goes flying towards right field.
You make the call.
Does It change if it was bang-bang where the runner arrived just around the same time as the ball? Would it change if the ball beat the runner and then he subsequently ran into the mitt that was in his way of progress?