Chief Aviation Electrician's Mate Greiner was a member of the crew of an EC-121 surveillance aircraft, serving with the U.S. Navy. On 15 April 1969, while on a surveillance mission over the Sea of Japan in support of the Korean truce, his aircraft was shot down. All 31 crewmen were reported missing. He was presumed dead on 2 May 1969.

Greiner was awarded the Purple Heart, the National Defense Service Medal and the Korean Defense Service Medal.