Exploding Target Ignites Sawmill Fire, Consumes 46,000 Acres

An exploding target has been confirmed as the cause of the Sawmill Fire, which devastated 46,000 acres of state trust land south of Tucson.

The off-duty Border Patrol agent involved was reportedly shooting at the target despite a ban on target shooting on state lands, according to law enforcement sources. State Land Department guidelines permit firearm discharge solely for lawful and licensed hunting activities.

While the Land Department didn’t clarify whether exploding targets are explicitly banned, they are prohibited on lands managed by the U.S. Forest Service and the Bureau of Land Management in Arizona and other Western states. The department’s website offers no specifics on this issue.

The Sawmill Fire, incurring costs of at least $5 million, spread rapidly due to high winds on April 23. Winds gusting up to 40 miles per hour and a fire watch contributed to the fire’s swift spread, said Chuck Wunder, chief of the Green Valley Fire Department. Wunder’s department received the first fire call at 10:58 a.m. and arrived on the scene at 11:11 a.m., by which time 300 acres were already ablaze.

Before being mostly contained, the fire crossed the Santa Ritas and Arizona 83, endangering the historic Empire Ranch and the 42,000-acre Las Cienegas National Conservation Area. Hundreds of nearby homeowners were placed on pre-evacuation notice, and various infrastructures were at risk. The blaze also temporarily closed a section of Arizona 83.

The Forest Service is currently investigating the fire’s origins but has refused to release records until legal reviews are completed. Likewise, the Pima County Sheriff’s Department and the State Land Department have not yet provided the requested information.

In another incident, the Forest Service is probing a smaller April 4 brush fire that torched 50 acres on Mount Lemmon. This fire was also believed to be connected to recreational shooting, based on eyewitness accounts and site activity. The Forest Service is seeking a “person of interest” in connection with this fire.

The Sawmill Fire was sparked by Tannerite, a binary explosive composed of ammonium nitrate and aluminum powder. Tannerite, inert when its components are separate, explodes upon mixing. This explosive, produced by Tannerite Sports LLC in Pleasant Hill, Oregon, is often used nationwide for target practice.

Tannerite creates a water vapor and a loud boom when shot with a high-power rifle. While the separated substances are unregulated, the mixed product falls under the jurisdiction of the U.S. Bureau of Alcohol, Tobacco, and Firearms. Transporting mixed Tannerite requires proper ATF permits or licenses.

The use of exploding targets has caused significant concern across the West. Forest Service officials attribute more than a dozen recent wildfires to these targets.