working as a mover

when working as a mover, especially those companies you get high salaries and pay no tax, you are expected to do some real heavy duty ranging from lifting a sofa bed to lifting a piano. In one situation me and another person were supposed to lift the piano. When lifting it to place it on the skid then the four wheeler, the other person injured his back due to poor posture. It was me and him alone on that job. I had to call my boss and tell him even though the guy insisted not to call him. The boss sent me another guy and still we couldn't lift the piano. The task was very difficult and needed more than two people , so I told my boss (the authority) I cant do this and he just told us to get back and he fired me and the guy with the injured back. The primary determinant was not only the fact that my coworker injured his back and made me fear to be injured my self, but the task itself was very difficult ( out of my individual ZPD).