Ok with the 2 different casings, I wouldn't read much into that yet. Living in the country before, having numerous family living on working farms..
It isn't unusual to throw open a window or door and fire at an intruding animal. I've done it a few times myself.
When my cousin sold the chicken farm and I was helping her pack up stuff, they moved the furniture out of her bedroom. The windows there faced the chicken houses.
It literally looked like a crime scene with casings we found under and behind things.
They could be from the murders, but the chances are good also one may not be.
ETA: It can also be a funny redneck thing for some men to throw open a window and target shoot at something. I've had idiot cousins do that.