Sgt. Butler was in the Army Air Forces, and flew as a waist gunner on a B-24 bomber in the Pacific.The Army Air Force had quite a few bases in the Pacific, where they attacked various Japanese positions throughout the war. He was awarded 5 Air Medals, which were typically given out on the completion of 5 missions, so he probably had flown 25 missions before he was killed.
There are a couple of different govt. records you can get on him, but probably won't get you any closer to your family connection.My guess is he was a co-worker, neighbor, or high school buddy of your grandmother.My mom kept a scrapbook of all the guys who were killed from my hometown, some she knew, others she didn't.
See message 10907 on this board, especially the section on Aircraft Crash Reports, if you want additional info. Contact me via email if you're interested in pursuing the govt. records angle, and I'll provide his WW2 service number, which you'll need to get govt. records.