Authorities said the gun used in the killing of Charlie Kirk may be a decades-old, untraceable rifle, authorities have said.

Prosecutors and officials identified the gun as a Mauser Model 98 .30-06 caliber bolt-action rifle, a type originally manufactured in Germany for military use during both World Wars. It may predate U.S. laws enacted in 1968 following President John F. Kennedy’s assassination, which required firearms to carry serial numbers or other identifying marks — making it harder for law enforcement to trace.

Authorities said the firearm belonged to the grandfather of Tyler Robinson, the 22-year-old Utah man accused of assassinating Kirk. Police allege Robinson may have deliberately chosen the rifle because it was difficult to trace. 

Robinson himself appeared to echo that reasoning in a message to his roommate just hours after the assassination. 

A report from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) notes that it is exceedingly rare for such rifles to be used in crimes. Most gun violence in America is carried out with pistols, while semiautomatic AR-15-style rifles have been used in some of the nation’s deadliest mass shootings.

Charlie Kirk throws hats to the crowd after arriving at Utah Valley University on Sept.10, 2025, in Orem, Utah. (Trent Nelson/The Salt Lake Tribune/Getty Images)

ATF and the Federal Bureau of Investigation Salt Lake City did not immediately respond to a request for comment from Fox News Digital.