A native of San Diego, California Captain Santarsiero attended Norwich University, where he was awarded a three-year Naval Reserve Officer Training Corps (NROTC) Scholarship. 2ndLt Santarsiero received his commission following his completion of Officer Candidates School in July 2021 and his graduation from Norwich University with a Bachelor of Arts in History in April 2023. In June 2023 2ndLt Santarsiero reported to Quantico, Virginia for the Basic Officers Course (BOC).
Following his graduation from the BOC in January 2023 2ndLt Santarsiero was designated an 0801 Field Artillery Officer and reported to Marine Detachment, Fort Sill, Oklahoma, for the Marine Artillery Officer Basic Course (MAOBC). While at Fort Sill, 2ndLt Santarsiero attended and graduated from the Joint Fires Observer School. Following his graduation from MAOBC in June 2023, 2ndLt Santarsiero was assigned the primary MOS of 0802, Field Artillery Officer, and reported to Battery A, 1st Battalion, 11th Marines in Camp Pendleton, California where he served as a howitzer platoon commander. From June 2023 to November 2023 2ndLt Santarsiero led two platoons through several battery, battalion, and service level exercises aboard Camp Pendleton and Marine Corps Air Station (MCAS) Yuma. Following Battery A's deactivation in November 2023 under Force Design 2030, 2ndLt Santarsiero reported to Battery T, 1st Battalion, 11th Marines where he was assigned as a Fire Direction Officer. In January 2024, 2ndLt Santarsiero reported to Marine Corps Mountain Warfare Training Center, Bridgeport, California, where he attended the Winter Mountain Leaders Course (WMLC). Upon successful completion of WMLC in February 2024, 2ndLt Santarsiero was assigned the additional MOS of 0942 Winter Mountain Leader. In April 2024, 2ndLt Santarsiero was promoted to his current rank of First Lieutenant.
In May 2024 1stLt Santarsiero deployed with Battery T, 3rd Battalion, 12th Marines to Okinawa, Japan in support of UDP 24.2. Following redeployment, 1stLt Santarsiero was assigned as the Battalion Fire Direction Officer for 1st Battalion, 11th Marine Regiment. In August 2024, 1stLt Santarsiero earned the additional MOS of 8012 Ground Safety Officer and reported to the G-10, Force Resiliency Directorate, 1st Marine Division to serve as the Risk Management Officer. In September 2024, 1stLt Santarsiero completed the Department of the Navy Ground Mishap Investigation Course (GMIC) and was assigned as the Director of Risk Management to the Commanding General, 1st Marine Division. From November 2024 to July 2025, 1stLt Santarsiero served on six Safety Investigation Boards (SIB's) providing subject matter expertise on mishap investigations and identifying causal factors for serious Marine Corps mishaps in which significant injury or fatality occurred. 1stLt Santarsiero spent several months liaising with local and federal law enforcement agencies, Marine Corps units, and Naval Safety Command personnel while investigating the causes of mishaps across 3 U.S. states. In June, 2026 1stLt Santarsiero reported to Battery I, 3rd Battalion, 14th Marines for duty as the Inspector-Instructor. In July, 2026 1stLt Santarsiero was was promoted to his current rank of Captain
1stLt Santarsiero's personal decorations include, the Navy and Marine Corps Achievement Medal.