CBS News anchor John Dickerson said Monday that the motive behind the assassination of Turning Point USA founder Charlie Kirk remains "elusive," despite reports about the alleged suspects leftist ideology."Five days after Charlie Kirks murder, the shooters motive remains elusive," Dickerson said on "CBS Evening News Plus. " "No writings left behind. Vague, secondhand testimony, that uncertainty and the risk of drawing sweeping conclusions suggests the murder may share similarities with recent violence, not driven by an obvious political ideology. The FBI recently recognized a new category: nihilistic violent extremism."Dickerson interviewed Matthew Kriner, director of the Institute for Countering Digital Extremism, who explained that nihilistic violent extremism is "driven by a lack of singular ideological framework" and carried out by individuals "who are fed up with the world [and] believe theres no political solution."CRIMINOLOGIST TELLS MSNBC SHE CAN'T FIND MOTIVE FOR CHARLIE KIRK'S KILLING IN BULLET CASING MESSAGESKriner added that the category also coincides with "neo-fascist accelerationism," defined as the push for societal collapse through violence, including terrorism.Though investigators have not confirmed a motive, FBI officials and Utah Gov. Spencer Cox said 22-year-old Tyler Robinson had become increasingly radicalized after embracing a "leftist ideology." Relatives and friends reported that Robinson moved further left politically after dropping out of Utah State University.Robinson had also reportedly showed disdain for Kirk prior to the shooting. Authorities reported references engraved on the ammunition used to kill Kirk, including one message that read, "Hey, fascist! Catch!"RETIRED FBI AGENT WARNS OF 'ASSASSINATION CULTURE' AFTER LEARNING KIRK SUSPECT LIVED WITH TRANS PARTNERSenior-level FBI officials also said Robinson was in a "romantic relationship" with a transgender partner who, according to a relative, "hates conservatives and Christians."Dickersons segment did not include this information.Fox News Digital reached out to CBS for comment but did not immediately receive a response.The FBI declined to comment.Robinson is accused of shooting and killing Kirk as the 31-year-old husband and father of two young children was speaking at a Turning Point USA event at Utah Valley University on Wednesday.CONSERVATIVE VOICES ERUPT AFTER CBS NEWS HOST TARGETS GOP RHETORIC IN WAKE OF CHARLIE KIRK ASSASSINATIONOn NBCs "Meet the Press," Cox said more details about the investigation would be revealed on Tuesday, though he stopped short of offering a clear motive behind the assassination.CLICK HERE TO GET THE FOX NEWS APP"The why behind this, again, we're all drawing lots of conclusions on how someone like this could be radicalized, and I think that those are important questions for us to ask and important questions for us to answer," he said.