(CNN) โ€” Charlie Kirk, a conservative political activist and co-founder of Turning Point USA, was killed Wednesday after being shot at an event at Utah Valley University, President Donald Trump wrote on his Truth Social platform. He was 31.

As Trump remade the Republican Party, Kirk embodied the partyโ€™s newfound populist conservatism in the social media age. Trump has credited Kirk with galvanizing and mobilizing the youth vote for him.

โ€œNo one understood or had the Heart of the Youth in the United States of America better than Charlie,โ€ the president wrote. โ€œHe was loved and admired by ALL, especially me, and now, he is no longer with us.โ€

Kirk, himself a college dropout, was influential with college students and young voters โ€” not only in helping to elect Trump to the presidency but also to inspire a new movement of conservative activists. His involvement began in the wake of the tea party movement and grew with Trumpโ€™s ascendance.

Having co-founded Turning Point in 2012 at the age of 18, Kirk was a prominent supporter of Trump who courted young voters and used his network of nonprofits to seek to turn out voters on campuses and churches for Trump in 2024.

Kirk frequently traveled to college campuses, speaking and taking questions from audience members in exchanges that often led to viral videos. Kirkโ€™s appearance at Utah Valley University on Wednesday was the first of a 14-city fall โ€œAmerican Comeback Tour.โ€

Kirk was answering a question at the event when a single pop was heard. Video taken by attendees shows the crowd screaming as Kirk recoiled in his seat and appeared to reach for his neck.

The scene after Charlie Kirk was shot on Wednesday. Credit: Trent Nelson/The Salt Lake Tribune / Reuters via CNN Newsource

Among those in attendance was former US Rep. Jason Chaffetz, a Utah Republican. He said on Fox News he was at the event with his wife, daughter and son-in-law. He said Kirk โ€œcame out, he was throwing hats, riling up the crowd,โ€ and then started taking questions before the shot rang out.

โ€œI was watching Charlie. I canโ€™t say that I saw blood. I canโ€™t say that I saw him get hit, but I did see him fall immediately backwards into his left,โ€ he said.

The American Comeback Tour had Kirkโ€™s signature โ€œProve Me Wrong Table,โ€ where he would urge those who disagreed with him to debate an issue.

Kirk traveled with a private security contingent, a Turning Point USA aide traveling on the tour told CNN, whether he was speaking to large rallies like the one in Orem, Utah, or at smaller events.

Kirk most recently appeared in the Oval Office in May, attending the swearing-in ceremony of Judge Jeanine Pirro as US attorney for Washington, DC.

The president and dozens of other Kirk allies โ€“ as well as Democrats who had sharp disagreements with him โ€“ posted well-wishes and calls for prayer online in the wake of the shooting.

President Donald Trump shakes hands with moderator Charlie Kirk during a Generation Next White House forum in Washington, DC, on March 22, 2018. Credit: Manuel Balce Ceneta / AP via CNN Newsource

Kirk argued Trump was saving the American dream

Kirk was known for debating college students about abortion rights, which he opposed; climate change, which he downplayed; and transgender rights, which he rejected. He frequently sought to rally young people around traditional gender roles. He also backed Trumpโ€™s mass deportation efforts.

Kirk spoke at the last three Republican conventions. In 2024, he said that marriage and home ownership were elusive for too many young Americans, and faulted former President Joe Biden.

โ€œUnder Biden, our young people own nothing and they are miserable. Donald Trump refuses to accept this fake, pathetic, mutilated version of the American dream,โ€ he said. โ€œDonald Trump is on a rescue mission to revive your birthright, one your grandparents and those before them gave everything to hand down to you.โ€

Kirk was an outspoken advocate for gun rights.

At an April 2023 Turning Point USA Faith event, he said that โ€œyou will never live in a society when you have an armed citizenry and you wonโ€™t have a single gun death.โ€

But, Kirk added, โ€œI think itโ€™s worth it. I think itโ€™s worth to have a cost of, unfortunately, some gun deaths every single year so that we can have the Second Amendment to protect our other God-given rights. That is a prudent deal. It is rational.โ€

Turning Point USA Founder Charlie Kirk speaks before Donald Trump arrives at the Turning Point Believers’ Summit in West Palm Beach, Florida, in July 2024. Credit: Alex Brandon / AP via CNN Newsource

He started in politics as a teenager

Kirk got his first experience in politics as a student at Wheeling High School in the northwest suburbs of Chicago, when he volunteered for the winning 2010 Senate campaign of Republican former Sen. Mark Kirk.

He earned national attention in 2012 when, as a high school senior, he wrote in Breitbart News that high school students were being indoctrinated by liberal textbooks. He briefly attended Harper College, but dropped out to become a full-time conservative activist, and went on to argue that college is unnecessary for many people.

Kirk and retired businessman and conservative activist Bill Montgomery co-founded Turning Point USA in 2012. The two had met when Kirk was 18, at a speaking engagement at Benedictine University that followed his Breitbart piece. The organization was quickly backed by a roster of major Republican donors, including Foster Friess.

He went on to become a best-selling author and well-known media personality who hosted a daily three-hour show.

In 2021, Kirk married Erika Frantzve, with whom he shared two young children.

This story has been updated with additional details.