HUMBOLDT, S.D. (AP) — Authorities say one person was killed in a South Dakota house explosion and two others were so seriously hurt that they were flown to a hospital. Capt. Josh Phillips, of the Minnehaha County Sheriff’s Office, says a bystander who spotted the house engulfed in flames reported the blaze around 7 a.m. and helped the victims. Several volunteer fire crews from the surrounding area rushed to the home, which is located just a few miles south of the town of Humboldt. The Sioux Falls Fire Department also responded, but the home was leveled.