Put a cooperative cow ahead of him in the alley, get her moving and onto the trailer and he will likely follow. I would not get in there to try to separate them,  just reload the cow at the destination as mentioned above. I would forget the shot. If you can get him in the chute to give him the shot you should be able to get him into the trailer without the shot.  Just have a cow ahead of him as Poverty Acres suggests.

I've tried loading a bull by himself and that took hours. Next time I put a cow ahead of him and the bull just followed her from the alley, through the chute, loading ramp and onto the trailer.  Once you get the cow moving the key is to keep them both moving. I have found a paddle that rattles works and a pat on the rump with that keeps most of them moving.

To the OP: I've found that Dr Temple Grandin's magic number of exactly 30" inside width for a loading ramp seems to work well with any animals I've had to load from heifers to bulls. 30" is small enough to keep smaller cattle from turning around yet wide enough to let a big bull slide through. What is it about your corral you are concerned about?  

Safety is #1 though. Not worth getting hurt. Good luck. 

Jim