Ability to shoot yourself with a shotgun is probably an unintended feature of game mechanic.
It works like this: if you have a shotgun with slightly bigger area of effect you can target a tile next to you thus putting yourself inside the weapons area of effect.
Target enemy, get shot yourself
Not much to complain you can do lots of other stuff aside a suicide shot
but i think guns could use some more versatility and shotgun is first on my list
i suggest changing how this weapon works by making it a arc blast radius starting from player
like the dnd spell cone of cold works