A top-notch Marine died recently while training at Camp Pendleton, California, to become a Recon Marine, Corps officials confirmed on Saturday.

Pfc. Michael P. Giannattasio was found unresponsive on Aug. 30 during a land navigation event at the Basic Reconnaissance Course at the School of Infantry (West), Training and Education Command said in a statement.

Emergency responders were unable to resuscitate Giannattasio, who was pronounced dead at the scene, the TECOM statement said. No further information was immediately available about how Giannattasio died. His command and the Naval Criminal Investigative Service are looking into the incident.

“The Marine Corps is in mourning and offer our deepest condolences,” the TECOM statement said. “We continue to support the family during this difficult time.”

The San Diego Union-Tribune first reported about Giannattasio’s death on Thursday. Giannattasio completed recruit training at Parris Island in April and received the “Iron Man” prize for scoring 600 points on both his Physical Fitness and Combat Fitness tests, according to the newspaper.

“Pfc. Giannattasio was an outstanding Marine who stepped up to the difficult challenge of earning a spot amongst our distinguished reconnaissance forces,” the TECOM statement said. “Though he will be deeply missed, he will always remain in our ranks. Once a Marine, always a Marine.”