SAN DIEGO — The Marine killed Tuesday in an explosion at a demolition range in Okinawa, Japan, was preparing to help destroy a World War II-era shell when it exploded, killing him and wounding two others on his team, III Marine Expeditionary Force officials said.

Officials are investigating the blast that killed Staff Sgt. John H. Roy III, 32, of Muscogee, Ga., and also wounded another Marine and a sailor, officials said Wednesday in a news release. The two wounded victims, who were not identified, were taken to the naval hospital in Okinawa for treatment, they said.

Roy was part of an explosive ordnance disposal team that was preparing the munition for destruction at Demolition Range 3 in the Central Training Area when it exploded at 11:15 a.m. March 24, they said. Range 3 has been used for disposal of unexploded ordnance since before Okinawa was reverted in 1972 to Japan control.

Roy, who enlisted in the Corps in 1994, was an EOD technician assigned to Headquarters and Service Battalion at Marine Corps Base-Camp Butler in Okinawa. He had deployed to Iraq last year. “Our thoughts and prayers go out to his family,” Col. Frank Simonds, the battalion commander, said in a statement. “He was an integral member of our unit and his contributions will be sorely missed.”

Roy’s personal awards and decorations include the Navy-Marine Corps Achievement Medal, Marine Corps Good Conduct Medal, Iraq Campaign Medal, Armed Forces Expeditionary Medal, Global War on Terrorism Expeditionary medal, Global War on Terrorism Service Medal, National Defense Service Medal, Navy Unit Commendation, Sea Service Deployment Ribbon and Marine Corps Overseas Service Ribbon.