While pulling and standing back 2 3/8” tubing on a truck mounted rig, the rig operator activated the traveling block and caused it to contact the crown of the derrick. The contact severed the drill line causing the block, the elevator links, and the tubing elevators to fall to the rig floor. The traveling block contacted the rod basket and tubing board prior to striking the tongs and landing on the rig floor. Upon impact with the floor, 2400’ of 2 3/8” tubing parted and fell into the well. The floor fell in a vertical position parallel to the derrick footing between the blowout preventers and the base section of the rig. The traveling block came to rest between the work floor and the derrick footing. The well was immediately secured. Contract employees were able to quickly evacuate the rig floor prior to the contact.