Born on November 8, 1978, in Shreveport, Louisiana, Jonas was known for a rare combination of fierce capability and irrepressible humor. A graduate of Caddo Magnet High School, he was remembered by those closest to him as a man who loved to laugh, who staged elaborate good-natured practical jokes, and who read constantly to better understand the world around him. He enlisted in the U.S. Navy in September 1996 and completed basic training at NTC Great Lakes, Illinois, that December.

Driven to serve at the highest level, Kelsall completed Basic Underwater Demolition/SEAL (BUD/S) training in 1997 and earned his Trident. He became one of the earliest members of SEAL Team 7, and his skill and leadership later carried him into the Naval Special Warfare Development Group, where he served as an officer among the nation's most elite operators.

Over a distinguished career, Kelsall deployed repeatedly in support of the Global War on Terror and was decorated many times over. His awards include the Legion of Merit, two Bronze Star Medals with Combat "V" for valor, the Joint Service Commendation Medal with Combat "V", three Navy and Marine Corps Commendation Medals, the Joint Service Achievement Medal, the Presidential Unit Citation, and the Combat Action Ribbon, among many others.

On August 6, 2011, Lieutenant Commander Kelsall was aboard the CH-47 Chinook helicopter, callsign Extortion 17, moving to reinforce a unit of U.S. Army Rangers engaged with the enemy in Wardak Province, Afghanistan. When insurgents struck the helicopter with a rocket-propelled grenade, all 30 Americans aboard were lost, including 17 from the Naval Special Warfare community. It remains the greatest single-incident loss of life in Naval Special Warfare history.

Jonas lived in Virginia with his wife, Victoria. He is remembered as a devoted husband, a loyal son and brother, and an adventurer who sought out the world and met it with a laugh. His courage, his intellect, and his joy left a mark on everyone who knew him.