That shotgun reference is a recollection of the day Bob's 12 gauge discharged as he climbed over a fence. About 1984. Silly fellow was hardly a hunter. I was so freaked to realise how close he'd come to blowing his head off I could barely speak but typical of the man, he ended up attempting to comfort and reassure me! No more shotgun after that.
On just re-discovering this poem in the ether I was tempted to clarify this incident by adding to its text, but I don't want to change what must have been an utterly spontaneous splurge of images from the eyelid cinema library ... I can't remember the Philip who wrote that poem but he seems close.