Gunnery Sergeant Mancilla was born in San Antonio, Texas. He enlisted in the United States Marine Corps on 26 November 2012, attending Recruit Training aboard MCRD San Diego, California. Upon completion of Recruit Training, he reported to School of Infantry-West, Marine Combat Training Battalion (MCT) aboard Camp Pendleton, California. Following MCT, Private Mancilla was ordered to the Defense Information School in Fort George G. Mead, Maryland to gain the primary Military Occupational Specialty of 4612, Combat Graphic and Reproduction Specialist. In July of 2013, Private First Class Mancilla reported to Combat Camera, Headquarters Battalion, Marine Corps Base Kaneohe Bay, Hawaii. In January of 2015, he was promoted to the rank of Corporal and returned to the Defense Information School in Fort George G. Mead, Maryland to attend the advanced Digital Multimedia Course. In December of 2016, he was promoted to the rank of Sergeant and received orders to Combat Camera, 2D Marine Division, Camp Lejeune, North Carolina. In October of 2017, he transferred to 1st Battalion, 6th Marine Regiment, 2D MARDVIV. During his tour, he deployed with V16 as the Combat Camera Chief, Black Sea Rotational Force, Romania, and the Marine Rotational Force - Europe, Norway supporting multiple operations and exercises in the EUCOM area of responsibility. In October of 2019, Sergeant Mancilla reported to 8th Marine Regiment, 2D MARDIV, deploying as the Communication Strategy and Operations Chief with Task Force - Southwest to Helmand Province, Afghanistan in support of Operation Freedom's Sentinel. In August of 2020, he was promoted to the rank of Staff Sergeant. In October of 2020, Staff Sergeant Mancilla attended the Intermediate Public Affairs Specialist Course, and was the honor graduate. In December of 2020, Staff Sergeant Mancilla received orders to Naval Amphibious Forces, Task Force 51, 5th Marine Expeditionary Brigade, as the Communication Strategy and Operations Chief. In August of 2021, Staff Sergeant Mancilla deployed as the Combat Camera and Public Affairs Chief with JTF-CR to Hamid Karzai International Airport, Kabul, Afghanistan in support of the Afghanistan NEO, the largest military airlift operation to date. In October of 2022 he deployed again as the Communication Strategy and Operations Chief, JTF-CR, in support of for the FIFA Word Cup in Qatar. During his time at Task Force 51/5th Marine Expeditionary Brigade, he supported CENTCOM's largest exercises, Eager Lion 22 and Bright Star 23, Additionally, he has supported MARCENT and NAVCENT as the lead Public Affairs chief for multiple component command level exercises in the CENTCOM area of responsibility. In January of 2024, he was promoted to his current rank. Gunnery Sergeant Mancilla currently serves as the Communication Strategy and Operations Chief, Task Force 51/5th Marine Expeditionary Brigade.