The 31-year-old, a Donald Trump ally and co-founder of the youth right-wing organisation Turning Point USA, was shot and killed at a Utah Valley University show on Wednesday.

After the shooting, the US President called Mr Kirk a “martyr for truth and freedom” and blamed the rhetoric of the “radical left” for the killing.

Suspected killer Tyler Robinson remains in custody following a 33-hour manhunt that ended when his father convinced him to surrender.

On Friday night, Erika Kirk delivered her first public remarks since the shooting, from the office where her late husband hosted his podcast.

Addressing her husband’s killer, she said: “You have no idea the fire that you have ignited within this wife.

“The cries of this widow will echo around the world like a battle cry.”

Erika Kirk, the wife of the late Charlie Kirk, lies draped across her husband's casket. [Erika Kirk/Instagram]

Erika Kirk, the wife of the late Charlie Kirk, lies draped across her husband’s casket. [Erika Kirk/Instagram]

Suspect in Charlie Kirk’s killing had become ‘more political’, authorities say

She also thanked Mr Trump, saying through tears that her husband loved the president, and vowed to keep her husband’s work alive, continuing his campus tour, radio show and podcast.

Here, a rally started at Belfast City Hall at 11am in memory of Mr Kirk.

Tyler Robinson was arrested in Utah. Utah Governor’s Office via AP

Tyler Robinson was arrested in Utah. Utah Governor’s Office via AP

Organisers described it as a “gathering for free speech”.

DUP leader Gavin Robinson said Mr Kirk was “hated by those who could not bear to see their ideology challenged”.

He said Mr Kirk’s “convictions were rooted in his faith” and “spoke more broadly to anyone who values truth, fairness and the foundations of a stable society”.

US authorities said the man accused of Mr Kirk’s assassination had earlier told relatives of his opposition to Mr Kirk’s viewpoints.

Sisters Clara Hetland (4), left, Haddie Hetland, centre (9), and Audra Hetland (6), of Surprise, Arizona, spend time at a makeshift memorial set up at Turning Point USA headquarters. AP Photo/Ross D. Franklin.

Sisters Clara Hetland (4), left, Haddie Hetland, centre (9), and Audra Hetland (6), of Surprise, Arizona, spend time at a makeshift memorial set up at Turning Point USA headquarters. AP Photo/Ross D. Franklin.

Tyler Robinson (22) had become “more political” in the run-up to the shooting and had indicated to a family friend afterwards that he was responsible, Utah governor Spencer Cox said.

Mr Cox also cited as key pieces of evidence engravings on bullets found in a rifle believed to have been used in the attack, as well as chatting app messages attributed to the shooting suspect which a roommate shared with law enforcement.

The Republican governor called Mr Kirk’s killing an “attack on the American experiment”, and he urged a new generation to “choose a different path”.

Tyler Robinson was arrested on suspicion of aggravated murder, felony discharge of a firearm causing serious bodily harm and obstruction of justice charges, according to a court affidavit.

A judge ordered that he be held without bail. Formal charges are expected early next week.

Robinson is believed to have acted alone and the investigation is ongoing, Mr Cox said.

Vice President JD Vance, right, Second Lady Usha Vance, centre, and Erika Kirk deplane Air Force Two, carrying the body of Charlie Kirk. AP Photo/Ross D. Franklin

Vice President JD Vance, right, Second Lady Usha Vance, centre, and Erika Kirk deplane Air Force Two, carrying the body of Charlie Kirk. AP Photo/Ross D. Franklin

Authorities have yet to reveal a motive, but they did describe evidence they said shed potential light on the killing.

That includes engravings on bullet casings recovered from the high-powered rifle believed to have been used in the attack, including one that said “Hey, fascist! Catch!”, Mr Cox said.

Mr Kirk was killed by a single shot in what police said was a targeted attack and Utah’s governor called a political assassination.

Mr Trump, who was joined by Democrats in condemning the violence, said he would award Mr Kirk the Presidential Medal of Freedom, the highest civilian honour in the US.

Vice president JD Vance and his wife, Usha, visited with Mr Kirk’s family on Thursday in Salt Lake City.

Mr Kirk’s coffin was flown aboard Air Force Two from Utah to Phoenix, where his non-profit political youth organisation is based.

Mr Trump told reporters he plans to attend Kirk’s funeral. Details have not been announced.