Just to clarify my brother/mother are nurses and know this shit, I've just done a few first aid courses BUT..
If there was bleeding, and it was life-threatening, then yes it should be stopped. Ideally you wouldn't move the injured person if a spinal injury to suspected, but if it's a case of...
As a first aider myself I think my concern would be more traffic coming down the road. Clearly it wouldn't be wise to move him as he has potentially serious spinal injuries. Checking the airway is clear and that he is breathing would have been my first port of call, followed by finding some way...