Sioux Falls Man Convicted on Three Unregistered Firearm Charges

Darren Kyle Stepp-Zafft, 30, of Sioux Falls, South Dakota, is going down for federal time after a jury convicted him on three counts of Possession of Unregistered Firearms. The verdict, handed down in a Sioux Falls federal courtroom, puts an end to a nearly year-long legal battle stemming from a raid that unearthed a virtual arsenal inside his apartment.

The charges carry a maximum penalty of 10 years in custody and/or a $250,000 fine, 3 years of supervised release, and a $100 special assessment to the Federal Crime Victims Fund. Each count stands alone, meaning the sentences could stack — and Stepp-Zafft could be looking at a decade behind bars when sentenced.

The trouble began December 10, 2015, when law enforcement officers descended on Stepp-Zafft’s Sioux Falls residence. They were hunting evidence of a firearm that had discharged into a neighbor’s apartment — a terrifying incident that sparked the investigation. What they found went far beyond a single rogue gun.

During the search, agents discovered two illegal firearm silencers, five illegal short-barreled rifles, and nine illegal destructive devices — components that could be readily assembled into functional grenades. The cache, described by ATF investigators as ‘combat-ready,’ painted a chilling picture of a man preparing for war, not living in a residential complex.

Stepp-Zafft was indicted by a federal grand jury on May 10, 2016. The case was jointly investigated by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, the Sioux Falls Police Department, and the South Dakota Division of Criminal Investigation. Assistant U.S. Attorney Jeffrey C. Clapper led the prosecution, methodically laying out evidence of illegal possession and assembly.

A presentence investigation has been ordered. Stepp-Zafft was remanded into the custody of the U.S. Marshals Service immediately following the verdict. No bond. No freedom. Just steel doors and a long wait for sentencing.

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