The FBI has questioned and released two people after the public shooting of conservative influencer Charlie Kirk, as a manhunt to find the killer continues.

US President Donald Trump said he was “filled with grief and anger” after 31-year-old Kirk was shot in the neck during a university appearance in Utah on Wednesday (US time).

Kirk, the CEO and co-founder of the conservative youth organisation Turning Point USA, was a close Trump ally and MAGA luminary.

The father of two was sitting under a small gazebo while addressing a packed crowd of students at Utah Valley University in Orem, south of Salt Lake City.

During his Q&A session, a single shot rang out and Kirk could be seen reaching up with his right hand as blood gushed from the left side of his neck.

Stunned spectators gasped and screamed before people started to flee.

US media said video footage appeared to show a person escaping across a rooftop shortly after the shooting.

Utah Department of Public Safety commissioner Beau Mason said the shot came “potentially from a roof”, with the suspect wearing “all dark clothing”.

“The only information we have on the suspect, the possible shooter, is taken from closed-circuit TV here on campus.

“But it is security camera footage, so you can kind of guess what the quality of that is.”

Footage appeared to show someone on the roof at the time of the shooting. Photo: X

The FBI said both “subjects” who were arrested after the shooting had since been released.

One was an older man who was seen being dragged away by police, according to the New York Post.

The second was standing about seven metres from Kirk when he was hit. That person’s mother told the Post her son, a fan of Kirk, was “super shaken” after travelling to Utah Valley Campus.

“He’s a great kid,” she said. “He was attending like any other college kid. He listens to him.”

FBI director Kash Patel posted on X: “The subject in custody has been released after an interrogation by law enforcement.

“Our investigation continues and we will continue to release information in interest of transparency.”

Charlie Kirk’s shooting has been condemned as a needless act of violence. Photo: AAP

In a video address on Wednesday night (US time), Trump said it was a “dark moment for America”.

He vowed to track down and punish the “monster” responsible and anyone else connected with the “political assassination”.

“My administration will find each and every one of those who contributed to this atrocity and to other political violence, including the organisations that funded and supported it,” he said.

During his address, Trump blamed the “radical left” for encouraging violence against those who did not share their political views.

He said the left had compared “wonderful Americans like Charlie to Nazis and the world’s worst mass murderers and criminals”.

“This kind of rhetoric is directly responsible for the terrorism that we’re seeing in our country today, and it must stop right now,” he said.

“An assassin tried to silence him with a bullet, but he failed because together we will ensure that his voice, his message and his legacy will live on for countless generations to come.”

Trump has ordered flags across the US to be flown at half-mast for the rest of the week.

Police smother the campus after the shooting. Photo: AAP

Kirk was speaking at a debate hosted by his nonprofit political organisation.

Immediately before the shooting, he was taking questions from the crowd about mass shootings and gun violence.

“Do you know how many transgender Americans have been mass shooters over the last 10 years?” an audience member asked. Kirk responded: “Too many.”

The questioner followed up: “Do you know how many mass shooters there have been in America over the last 10 years?”

“Counting or not counting gang violence?” Kirk asked.

Then a single shot rang out.

The event had been met with divided opinions on campus. An online petition calling for university administrators to bar Kirk from appearing received nearly 1000 signatures.

Kirk personified the pugnacious, populist conservatism that has taken over the Republican Party in the age of Trump.

He was an unabashed Christian conservative who often made provocative statements about gender, race and politics.

A backer of Trump during the President’s initial 2016 run, Kirk took Turning Point from one of a constellation of well-funded conservative groups to the heart of the right-of-centre universe.

Turning Point’s political wing helped run get-out-the-vote efforts for Trump’s 2024 campaign, trying to energise disaffected conservatives who rarely vote.

Trump won Arizona, Turning Point’s home state, by five percentage points after narrowly losing it in 2020. The group is known for its events that often feature strobe lighting and pyrotechnics. It claims more than 250,000 student members.

Kirk started as an unofficial adviser during Trump’s 2016 campaign and more recently became a confidant.

Kirk showed off an apocalyptic style in his popular podcast, radio show and on the campaign trail. During an appearance with Trump in Georgia last autumn, he said Democrats “stand for everything God hates”.

Kirk called the Trump versus Kamala Harris choice “a spiritual battle”.

He was a regular presence on college campuses. Last year, for the social media program Surrounded, he faced off against 20 liberal college students to defend his viewpoints, including that abortion is murder and should be illegal.

The author of several books, including one on the US Second Amendment, Kirk was a staunch supporter of gun rights.

“I think it’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,” Kirk said at a Turning Point event in Salt Lake City in 2023, adding that gun deaths could be reduced but would never go away.

Kirk announced he was organising buses to travel to Washington to back Trump on January  6, 2021, and later invoked the Fifth Amendment rather than answer questions from the Jan 6 subcommittee.

Also in 2021, as he stepped up criticism of the Black Lives Matter movement on college campuses, Kirk called George Floyd, the black man whose 2020 murder at the hands of Minneapolis police sparked protests that roiled Trump’s last full year in office, a “scumbag”.

But as younger voters shifted right in 2024 and Trump ran up a five-point margin of victory in Arizona, Kirk and his allies claimed vindication of his view of a sharp-elbowed, culture-war-oriented conservatism.

Kirk’s evangelical Christian beliefs were intertwined with his political perspective, and he argued that there was no true separation of church and state.

He also referenced the Seven Mountain Mandate that specifies seven areas where Christians are to lead — politics, religion, media, business, family, education and the arts, and entertainment.

Kirk argued for a new conservatism that advocated for freedom of speech, challenging Big Tech and the media, and putting working-class Americans beyond the nation’s capital at the centre of priorities.

“We have to ask ourselves a question as a conservative movement: Are we going to revert back to the party of the status quo ruling class?” he said in his speech opening the Conservative Political Action Conference in 2020.

“Or are we going to learn from what I call the MAGA doctrine? The MAGA doctrine, which is a doctrine of American renewal, revival, one that America is the greatest country in the history of the world.”

Admirers stressed that, for all of Kirk’s confrontational rhetoric, he relished debate and the free exchange of ideas.

Kirk was married to podcaster Erika Frantzve. They have two young children.

-with AAP