According to Ancestry.com.
Alabama Soldiers in the Korean War, 1950-1952, Cpl. Joseph H. Mayo was killed on December 7, 1950, while serving with Headquarters Company, Headquarters Battalion, 1st Marine Division. Cpl. Mayo was the son of Mr. and Mrs. George H. Mayo of York.
Cpl. Mayo's is still listed as MIA, a rememberance can be found on the Courts of the Missing in Hawaii. That listing can be seen at this site:
https://www.findagrave.com/memorial/96467003/joseph-haynes-mayo.