First Sergeant Matthew Shea enlisted in the Marine Corps in September 2000. Upon graduation from Marine Corps Recruit Depot San Diego, California, and Marine Combat Training at Camp Pendleton, California, he reported to Field Artillery School at Fort Sill, Oklahoma.
In 2001, upon graduating as a Field Artillery Cannon Crewman, he reported to his active-duty station at Tango Battery, 5th Battalion, 11th Marines, 1st Marine Division, Camp Pendleton, California. First Sergeant Shea deployed in 2002 to the Western Pacific and supported Operation Anaconda in Afghanistan in the Arabian Sea. In 2003, he deployed once more with Tango Battery as a Gunner for the M198 Howitzer, providing Counter Battery Support during Operation Iraqi Freedom. Upon returning from Iraq, he attended and completed Howitzer Section Chief School at Camp Pendleton.
In 2004, First Sergeant Shea left active duty and pursued his civilian career, working as a Heavy Equipment Operator from 2004 to 2007. In 2007, he gained full-time employment with the Federal Bureau of Prisons as a Correctional Officer at the Federal Medical Center in Rochester, Minnesota.
In July 2007, First Sergeant Shea affiliated with the United States Marine Corps Reserve, joining Air Operations Company, Marine Wing Support Squadron Detachment in Fort Snelling, Minnesota. He then attended the Fire Protection Apprentice Course at Goodfellow Air Force Base, Texas; where he earned a second Military Occupational Specialty of 7051, Aircraft Firefighting and Rescue Specialist. From 2008 to 2019, First Sergeant Shea served as Crash Fire Rescue Inspector Staff Noncommissioned Officer in Command, Company Gunnery Sergeant, Headquarters & Support Company 1st Sergeant, and Air Operations Company 1st Sergeant.
From May 2019 to May 2021, First Sergeant Shea served as Company First Sergeant for Delta Company, 4th Recon Battalion, 4th Marine Division in Albuquerque, New Mexico. In May 2021, First Sergeant Shea assumed duties as Company First Sergeant for Echo Company, 2d Battalion, 24th Marines, 23d Marine Regiment, 4th Marine Division, in Granger, IA.