One shot turned a day into chaos, grief, and mounting political outrage when an unknown shooter killed controversial right-wing influencer and Trump ally Charlie Kirk onstage during an event at a university in Utah.

The shooter remains on the run, as law enforcement try to piece together what took place on the day.

A range of experts have also chipped in on everything from the kind of bullet used to where the shooter was likely standing.

So far, much is speculation, but a picture is beginning to come together, even if it remains a sketch so far.

Authorities believe the killer was on top of the roof of one of the university buildings.

After firing the fatal shot, they jumped down and fled into a nearby neighbourhood.

CNN believes the shooter pulled the trigger atop the building of the Losee Centre, about 135 metres from where Kirk was onstage.

An audio forensics expert, analysing the sound of the bullet, told CNN it was probably fired from about 150 metres away.

What was the weapon used?

Authorities have recovered a rifle they believe is the murder weapon.

Its details have not officially been released, but CNN quoted a law enforcement official saying the gun is a Mauser bolt action .30-06 calibre rifle with a long-distance scope.

The official also said a single shell casing remained inside the bolt mechanism.

The aforementioned audio forensics expert, Rob Maher, said the bullet had been faster than the speed of sound, travelling at an estimated 800m/s.

That bullet could only have come from a high-powered rifle, he said, not a handgun.

How difficult was the shot?

Theories have emerged online about the killer being a “professional” marksman of some sort.

However, firearms experts have played down that angle.

“He didn’t have to be highly trained as a sniper to make that shot from 200 yards (180 metres), because 200 yards with the right rifle and the right optics is not that far,” former FBI supervisory special agent Dennis Franks told The Independent.

But he also said hitting a target of that distance outside a shooting range was vastly different to a crowded public setting, requiring a level of skill or plain luck.

“To do it under the stress of a live situation, he was either skilful or lucky,” said Franks.