Authorities in southeast Iowa are trying to determine what killed a man who had been missing more than three months.The body of a missing Ottumwa man was found by children in the brush behind a grocery store in Ottumwa on Wednesday. 38-year-old Brian Ferguson hadn’t been seen since May. The cause of death is still unknown. Weeks ago, a gym bag containing some of Ferguson’s clothes was found under a railroad bridge. It had been feared Ferguson had jumped or fallen from the bridge and drown.