17-year-old Terry Grant Scott is now in the Killeen City Jail.
Police arrested him Tuesday afternoon.
25-year-old Army Specialist Austin James Sampson, of Bliss, died last week. He was shot outside a Texas convenience store.
Sampson deployed in support of Operation New Dawn from August 2010 to August 2011.
Before that, Sampson deployed in support of Operation Iraqi Freedom from November 2007 to January 2009.
Sampson's awards and decorations include the Army Commendation Medal, two Army Good Conduct Medals, National Defense Service Medal, Iraqi Campaign Medal with three campaign stars, Global War on Terrorism Service Medal, Army Service Ribbon, and Overseas Service Ribbon.
He was assigned to Fort Hood, Texas in 2006.