Supporters of slain right-wing activist and Trump ally Charlie Kirk said they oppose stricter gun laws, even after the 31-year-old was shot dead at Utah Valley University this week.

Authorities confirmed on Friday that the suspected shooter is in custody, though they have not disclosed how he obtained the high-powered rifle later found in nearby woods.

Utah, where the killing occurred, has some of the loosest gun laws in the United States.

Adults over 20 can carry firearms without permits, and students with concealed carry permits are allowed to bring weapons onto college campuses.

At a vigil Thursday night, several mourners echoed Kirk's own defense of the constitutional right to bear arms.

"It wouldn't have changed anything. When there's a will, there's a way. People get guns, no matter what," said 18-year-old electrician Boeden Seitzinger, who witnessed the shooting.

"That's not what Charlie would have wanted. You can't blame the gun. It's the person holding the gun who's at fault."

Kirk was a staunch Second Amendment supporter.

He once argued: "I think it's worth it 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."

Ongoing controversy

The United States has the highest gun fatality rate of any developed country.

More than 16,000 people died from gun violence last year, not counting suicides, according to the Gun Violence Archive.

For some, Kirk's death reinforced their belief in gun ownership.

"Utah is a little bit of the Wild West. When everybody carries a gun, you behave yourself," said Reed Fansworth, 73.

"There's so many guns. Even if we tried to take them away, we wouldn't be able to take them all," said Leah Marett, 25.

"Innocent people would be defenceless."