Authorities have released the names of the three people killed in plane crash Monday evening near the Grace Airport.  Norman Gunderson, his 16-year-old son Isaac, and Casey Crane were all killed when their private aircraft crashed. Norman and his son were both from Menan and Crane was from Grace. Authorities say Norman was the pilot of the aircraft. Sheriff Ric Anderson says the plane went down around 5:45 p.m. at a private landing strip two miles north of Grace. Responding officers to the scene discovered three people dead inside the aircraft. There is no word from investigators on what direction the airplane was traveling or its point of origin before Monday’s crash. On Tuesday morning the National Transportation Safety Board joined the Caribou County Sheriff’s Office in investigating what caused the plane to crash. The NTSB's regional office in Washington says that an air safety investigator, is in Grace going through evidence.