The rifle that federal investigators believe was used in the shooting that killed conservative activist Charlie Kirk contained ammunition inscribed with anti-fascist messaging, shedding light on the suspect's motive.Utah Gov. Spencer Cox confirmed the messaging at a news conference Friday, saying investigators discovered inscriptions on casings found with a bolt-action rifle near the Utah Valley University campus, where Kirk was killed during an event.One used casing and three unused casings contained the writings, Cox said.News of the ammunition inscriptions was first shared on social media Thursday morning in a preliminary bulletin attributed to the Bureau of Alcohol, Tobacco, Firearms and Explosives.SECRET SERVICE UNDER PRESSURE: WHAT KIRKS ASSASSINATION MEANS FOR TRUMPS SECURITYAccording to the bulletin, circulated on X by political commentator Steven Crowder, federal officials recovered a .30-06 caliber Mauser rifle in the woods that contained "engravings," including messaging expressing anti-fascist ideology and other messages.Fox News Digital confirmed the veracity of the ATF bulletin through talking to multiple sources, but the sources stressed on Thursday that the information was preliminary.DEMS, GOP LAWMAKERS JOIN FORCES TO CONDEMN POLITICAL VIOLENCE AFTER CHARLIE KIRK SHOTThe information about the firearm surfaced nearly 24 hours after Kirk, 31, was shot and killed during a speaking engagement in Utah. Both his graphic death and the scant public information revealed in the early hours of the investigation into his killing left the nation reeling and revived heated debate about political violence in the U.S.Law enforcement officials worked frantically in the aftermath of Kirk's death to track down and arrest the gunman, who they announced Friday was Tyler Robinson, a 22-year-old Utah man.Cox on Friday called the shooting a "political assassination."WHAT IS A BOLT ACTION RIFLE? WHAT WE KNOW ABOUT THE GUN USED TO KILL CHARLIE KIRK"This is certainly about the tragic death, assassination, political assassination of Charlie Kirk, but it is also much bigger than an attack on an individual," Cox said. "It is an attack on all of us. It is an attack on the American experiment."FBI Director Kash Patel laid out the timeline of the investigation Friday, saying it took the FBI and Utah law enforcement 33 hours to make an arrest. Patel said authorities made "historic progress" in such a short duration of time.The FBI's Salt Lake City Field Officereleased an image Thursday of a man they had said was a "person of interest" in Kirk's death and asked the public for help identifying him. The bureau also announced it was offering a $100,000 reward for information leading to his capture. Cox said a tip from a family friend of Robinson's led to his arrest.