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

Officials and prosecutors revealed that the firearm in question is a Mauser Model 98 .30-06 caliber bolt-action rifle. Originally crafted in Germany for military purposes during the World Wars, this type of rifle might have been produced before the implementation of U.S. laws in 1968. These laws, established after President John F. Kennedy’s assassination, mandate that firearms have serial numbers or other identifiers, which complicates tracing efforts for law enforcement.

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.