Charlie Kirk, a right-wing activist and commentator who became a household name in the United States as an outspoken ally of President Donald Trump, has been shot and killed at a Utah college event.

As the CEO and cofounder of the conservative youth organisation Turning Point USA, the 31-year-old Kirk attracted millions of viewers online for his outdoor debates on US college campuses.

Video of the shooting circulating on social media showed Kirk speaking to a large outdoor crowd and, moments later, falling off his chair with his hands on his neck after a loud crack that sounded like a gunshot.

He was pronounced dead after being brought to hospital in critical condition.

Utah authorities said Kirk was killed with a single shot that likely came from the rooftop of a nearby building in

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