On March 22, 2008, Jefferson was killed near Sperwan Ghar, Afghanistan, when the vehicle he was traveling in encountered an improvised explosive device (IED).

Born in Norfolk, Virginia, Jefferson enlisted in the United States Marine Corps following graduation from Lake Taylor High School in 1991.

After four years serving in the 2nd Reconnaissance Battalion at Camp Lejeune, North Carolina, he decided to enlist in the United States Air Force and become a combat controller, and upon graduation was assigned to the 21st Special Tactics Squadron at Pope AFB, North Carolina. For nearly five years, Jefferson served proudly as a member of Silver Team before moving into a highly coveted position in the Integrated Survey Program. For two years he honed his skills as an expert surveyor conducting multiple classified survey missions throughout the globe.

In 2002, Jefferson was selected to become an instructor at the Combat Control School, also located at Pope AFB. His expert instructor skills helped develop a new crop of young and aspiring airmen, significantly increasing the number of much needed graduates.

In July 2006, he returned to the 21st Special Tactics Squadron during a time of war and became an outstanding addition to the operations staff. He promptly picked up duties as the Non-Commissioned Officer in Charge (NCOIC) of Exercise and Plans, primarily responsible for all Joint Forcible Entry Exercises conducted at Fort Bragg, North Carolina.

In October 2006, Jefferson deployed for nearly six months as the NCOIC of the Special Tactics Assault Zone and Reconnaissance team. He conducted multiple operations throughout Iraq, Afghanistan, Qatar, Djibouti, Kenya, and other classified locations in the Horn of Africa. Following this deployment, he was selected as an element leader on Blue Team. During this time, he earned Distinguished Graduate honors from the Non-Commissioned Officer Academy and earned joint terminal attack controller combat mission ready status.

In January 2008, Jefferson once again volunteered to deploy to help fight the War on Terror. He deployed to Afghanistan in support of Operation ENDURING FREEDOM. It was on this deployment to Afghanistan that he was killed in action.

Technical Sergeant Jefferson's awards and commendations include the Bronze Star Medal, the Purple Heart, Air Force Commendation Medal with Valor, Air Force Achievement Medal with three oak leaf clusters, Global War on Terrorism Medal and the Armed Forces Expeditionary Medal.

His Bronze Star Medal Citation reads:

Technical Sergeant William H. Jefferson Jr. United States Air Force, distinguished himself by exceptionally meritorious service as Joint Tactical Air-Traffic Controller, for Special Forces Operational detachment Alpha (SFODA) 3332, Special Operations Task Force-32, Kandahar Airfield, Afghanistan, in support of Operation ENDURING FREEDOM (OEF) from 21 January 2008 to 22 March 2008. During this period, Sergeant Jefferson provided superior air asset information to the Detachment Commander for several joint operations within the Helmand Province, Afghanistan. His extensive knowledge enabled the detachment to operate with Close Air Support (CAS) on the battlefield and synchronize combat operations enabling the SFODA and Task Force-10 to successfully accomplish critical shaping and support operations allowing the Task Force (TF)-10 to enter and provide Humanitarian Assistance to small villages such as Khakesh Kariz. Sergeant Jefferson's communications skills assisted TF-10, to successfully execute their assigned missions as part of these operations. His continual interaction and advice ensured the success of Operational Detachment Alpha (ODA) 3332 and TF-10. The success of the detachment was recognized by the Combined Joint Special Operations Task Force-Afghanistan Commander. Sergeant Jefferson's composure while establishing a landing zone allowed ODA 3332 to Medical Evacuation personnel wounded in an Improvised Explosive Device strike. The CAS that Sergeant Jefferson controlled helped ensure the quick recovery evacuation of all wounded personnel. Sergeant Jefferson's resourcefulness and ingenuity in an austere environment enabled the detachment to communicate and coordinate CAS through multiple echelons utilizing a wide array of close air support systems. Sergeant Jefferson's unparalleled dedication ensured the detachment was well versed in call-for-fire related subjects. His extensive planning, development, and execution of an informative and concise communication program led to the overall combat effectiveness and survivability of the detachment to ensure the safe return of all team members. On 22 March 2008, in Kandahar Province, Afghanistan, Sergeant Jefferson made the ultimate sacrifice and gave his life in defense of his country. His actions are in keeping with the finest traditions of military service and reflect distinct credit upon himself, Special Operations Task Force-32, the Combined Joint Special Operations Task Force-Afghanistan, Special Operations Command Central, and the United States Air Force.