A Marine was killed Sunday and 21 others injured when a military helicopter carrying 22 people went down at Bellows Air Force Base, Hawaii, NBC News reported. In a brief statement, the Marine Corp. said 22 people were aboard the MV-22 Osprey from the 15th Marine Expeditionary Unit when it had a "hard-landing mishap" during a training exercise. Witnesses say three aircrafts doing rotations in the sky swopped toward the ground but only two came back up. Within seconds, black smoke could be see, they said. Twenty-one people taken to hospitals for assessment and treatment. The 15th Marine Expeditionary Unit, which is in Hawaii for a seven-month deployment, is based at Camp Pendleton in San Diego.