Thank you kindly.
I see Roy being pretty specialised for messy close combat, so the kind of raw stopping power you'd associate with a double-barrel shotgun seemed to be more up his alley, whereas a sniper rifle would be more Haley (assuming she gets her hands dirty) or even Belkar's weapon of choice. (Modern Belkar might also prefer knives just for their... personal qualities.)
As a barely-visible easter-egg, you can also see Belkar's photo on Celia's clipboard, by the way.