It was in Nara which is a reasonably big city but has lots of surrounding rural areas. According to NHK, police are saying it may have been a shotgun (the article has been edited multiple times and it's even less sure of that then when I left my comment).
If it was a shotgun it certainly looks modified if it's a shotgun.
Yeah I just saw the photo. I guess that was just the first impression they had when they were asked by the news?
I'm not sure hunting deer in Nara is allowed (it IS known a "deer city" and deer freely roam the streets. Maybe permitted outside of the city), but of all places where someone could have a shotgun - Nara is definitely one of them.