The US is on edge after conservative activist Charlie Kirk was killed today. 

The Donald Trump ally died after being shot in the neck at a campus event at Utah Valley University.

The shooter remains on the run after reportedly fleeing from a rooftop.

US correspondent Jonathan Kearsley says this incident is another watershed moment in the history of American gun violence.

"We've seen politically motivated attacks in Washington DC, we've seen the shootings of Minnesota senators, Minnesota politicians earlier this year - and now we're seeing a conservative commentator assassinated in full view of the public."

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