Sergeant Major Mejia was born in Los Angeles, California and raised in his hometown of San Diego, California. He enlisted in the Marine Corps and attended recruit training in India Company, 3rd Recruit Training Battalion, Marine Corps Recruit Depot, San Diego, California in July 2004. He reported to the School of Infantry, Camp Pendleton, California, for Marine Combat Training. He was then assigned to Fort Knox, Kentucky, for military occupational school (MOS), where he earned the MOS of 1812 - Armor Marine.
Upon school completion, Private First Class Mejia reported for duty to Company A, 4th Tank Battalion, Miramar, California in March of 2005. In June 2005, he was promoted to the rank of Lance Corporal and in April 2006, he augmented to Active duty. He was then assigned to Company D, 1st Tank Battalion, Marine Corp Air Ground Combat Center, Twenty-nine Palms, California, where he served as an M1A1 Abrams Main Battle Armor Marine Gunner. In April of 2007, Corporal Mejia was hand-selected from the Armor Marines in Company D to join the 13th Marine Expeditionary Unit, where he deployed to Iraq in support of Operation Iraqi Freedom. During this time, he served as an Armor Marine Gunner for an M1A1 Abrams Main Battle Tank, contributing to several clearing and over-watch missions for 3rd Battalion, 5th Marines in the cities of Al-Fallujah and Al-Karmah, from April 2007 to November 2007.
In October of 2008, he was deployed again to Iraq in support of Operation Iraqi Freedom in Sahl-Sinjar, Ninawa Province. During this time, he served as an Armor Marine Gunner for the Company Executive Officer, providing screen lines along the Syrian border. Towards the end of the deployment, he played a vital role in assisting Company B in sending all U.S. military Tanks out from Iraq. Sergeant Mejia later transitioned to serve in the role of a Squad Leader for a Quick Reaction Force in Al-Taqaddam, Iraq, for the I Marine Expeditionary Force where he conducted multiple Tactical Recovery of Personnel Missions -- from October 2008 to April 2009. In October 2010, Sergeant Mejia again deployed to Afghanistan in support of Operation Enduring Freedom as a provisional route clearance platoon from October 2010 to April 2011. During this time, Sergeant Mejia served as the vehicle commander for the lead vehicle of the route clearance platoon, coordinating with multiple adjacent units to clear routes along the Helmand Province in the city of Marjah. His vehicle contributed to finding eight improvised explosive devices (IEDs) accumulating to over 20 IEDs found for his platoon during this deployment.
In January 2012, Sergeant Mejia reported to Marine Corps Recruit Depot, Parris Island, South Carolina for Drill Instructor Duty, Class 2-12. Sergeant Mejia then reported to 3d Recruit Training Battalion, Company K, where he served five cycles as a green belt Drill Instructor and one as a Senior Drill Instructor. During this time, he had the pleasure of training, mentoring, and transitioning over 300 young men to become United States Marines. In January 2014, he was promoted to the rank of Staff Sergeant. In March of 2014, Staff Sergeant Mejia reported to the Combat Training Tank to serve multiple billets as a Marine Corp Instructor Trainer Water Survival, Chief Instructor for Marine Corp Water Survival School, and Staff Non-Commissioned Officer In Charge. During this time, he had the opportunity to train over 1,000 young men and women to qualify for Water Survival Basic, Water Survival Intermediate, and Marine Corps Instructor Water Survival.
In April 2015, Staff Sergeant Mejia reported to 1st Tank Battalion, Company A, where he served numerous billets from Platoon Sergeant, Platoon Commander, Company Master Gunner, Tank Leader, and Company 1stSgt. In December 2017, he was promoted to the rank of Gunnery Sergeant. In May 2018, Gunnery Sergeant Mejia reported to Inspector-Instructor duty with 4th Tank Battalion, Company B, where he served as the Inspector-Instructor Training Chief. During this time, Gunnery Sergeant Mejia was responsible for building training plans for the reserve component focused on creating lethal Armor Marines by evaluating tactics during Tank Gunneries. During this time, he played a vital role in the Deactivation of Tanks and Tank units - a historical moment for the Marine Corps.
In May of 2021, Gunnery Sergeant Mejia was frocked to his current rank of First Sergeant. In June of 2021, he received orders to Marine Wing Support Squadron 171, Company B. During this time, First Sergeant Mejia served as the Senior Listed Advisor for Company B, assisting in restructuring the Squadron and producing a more efficient deployable unit. He was also responsible for the accurate accountability and effective training for over 10 exercises spread throughout the INDO-PACIFIC region.
In July of 2024, First Sergeant Mejia received orders to Marine Corps Recruit Depot San Diego to serve has the Senior Enlisted Leader for Second Recruit Training Battalion, Company F. In October of 2024, First Sergeant Mejia was appointed to his current billet of Sergeant Major for First Recruit Training Battalion. In December of 2024, he was promoted to his current rank of Sergeant Major.
Sergeant Major Mejia's awards include the Purple Heart, Navy, and Marine Corps Commendation Medal with two gold stars, Navy and Marine Corps Achievement Medal, Combat Action Ribbon, and Drill Instructor Ribbon.