The Korean War-era building was filled with close to $1 million in equipment and uniforms for the 82nd Airborne Band.
It happened in the 82nd Airborne Division area off Longstreet Road and Keerans Street. A passerby reported the fire just after 4:30 p.m.
Images from Chopper11 HD show the fire quickly engulfed the wooden and sheet metal building.
The roof of the structure collapsed as fire crews from five counties helped Fort Bragg officials battle the flames.
Fort Bragg PAO Col. Kevin Arata says the roughly 50 to 60 band members left the building around 3:30 p.m. after practicing their patriotic concert that is part of the centerpiece of Fort Bragg's Fourth of July celebration.
Officials say no one was inside the building when the fire happened and it is unclear at this time how the blaze started.
Band members returned from Afghanistan eight weeks ago to prepare for this weekend's concert.
"Paratroopers can pull it all together," said Lt. Gen. Frank G. Helmick, the commander of the 18th Airborne Corps and Fort Bragg, when told of the incident. "They will not fail."
There was an urgent need for all types of instruments, music stands, sheet music and other music equipment - a need that was quickly met by a number of schools and citizens.
Despite their loss, band members say their show will go on as scheduled thanks to everyone's help.