The first shots fired by Stephen Paddock from the 32nd floor of the Mandalay Bay Hotel sounded like nothing more than fireworks.
But as Norfolk troopers Ross Woodward, Chris May and Stuart Finlay were to find out, they were the spark for 'pure chaos'.
The trio, from the 1st The Queen's Dragoon Guards, based at Swanton Morley, had just left the Tropicana, a hotel facing Mandalay Bay, when the gunfire began and the victims began falling to the ground.
'Everyone was screaming and getting shot,' said Trooper Woodward. 'But the training kicked in and we ran to where everyone else was running from.
The soldiers were on leave after taking part in a training deployment in the Mojave Desert.
'We didn't know where the gunman was,' Trooper Woodward added. 'We didn't know if he was on the floor or in the hotel but we attended the casualties that we could see directly in front of us.'
The soldiers split up and began treating as many people as they could, using t-shirts, sweaters and towels to apply pressure to gunshot wounds.
They waited with each person they treated until they could get them into someone's car to go to hospital or into an ambulance.
Away from the main concert area, Troopers Dean Priestly, James Astbury and Zak Davidson, were also desperately trying to help victims.
Trooper Priestly said: 'We were at the triage point so it was mass casualties. I can't put a number on how many we helped. It was a matter of grabbing someone injured, helping them to the front and getting them to the paramedics then going back, finding someone else and helping them.'
The shooting lasted for almost 10 minutes and by the time it came to an end 58 people had been killed and more than 500 had been injured.
The actions of the soldiers earned them praise and thanks from Prime Minister Theresa May.
'At the time it was reaction,' added Trooper Priestly. 'You didn't think about anything else but once you sit back after you realise what you've just been through it hits you like a brick wall. But you also have this sense of accomplishment that you've helped people and you've helped to possibly make a big difference.'
What happened on the day?
On October 1 Stephen Paddock, 62, stood in his hotel room on the 32nd floor of the Mandalay Bay Resort and Casino in Las Vegas and opened fire on concertgoers at an outdoor music festival.
To the thousands of people on the ground the first gunshots at around 10.05pm were thought to be fireworks.
But when the second burst erupted the injured began falling where they stood, while others ran.
Bullets rained down on concertgoers for almost 10 minutes as they desperately tried to escape, making the spilt-second decision of whether to run or hide.
When the shooting finished 58 people had been killed and more than 500 injured. Mr Paddock was later found dead in his hotel room after turning one of his guns on himself.
American authorities are now trying to determine what caused an American citizen to commit an act that has been labelled by many as the worst mass shooting in US history.
Who are 1st The Queen's Dragoon Guards?
The Queen's Dragoon Guards, based in Swanton Morley, is the Cavalry Regiment of Wales and the Border Counties and has a long and distinguished history dating back 328 years.
According to the Ministry of Defence they are one of the most operationally experienced regiments in the Army and have been deployed during the Gulf War, Iraq War and multiple times in Afghanistan.
Each soldier undergoes an enhanced two week first aid course, which trains them to deal with trauma and injuries caused by gunshots and explosives.
At the time of the Las Vegas shooting they had been visiting America as part of a training exercise called Diamondback which takes place in the Mojave desert at Fort Owen.
The soldiers spent 21 days training alongside the American Army and tested their ability to handle battlefield casualties during live exercises.
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