An Iraq veteran who stole a pick-up truck during the Las Vegas shooting to drive victims to the hospital has released a text message conversation he shared with the car's owner.

Taylor Winston, 29, was at the Route 91 Harvest country music festival with friends when Stephen Paddock began spraying the crowd with automatic gunfire from a nearby hotel.

Three days after the worst shooting in US history, the truck's owner sent the ex-marine the message: "Hey Taylor told you might have the keys to my truck??

"All I won't [sic] is the key. Other then that it's all water under the bridge to me and hows the people you hauled doing?"

Mr Winston replied: "I have em for ya. When do you want to meet for em? We're at the Monte Carlo.

"I took about 30 critically injured to the hospital. Your truck was extremely important saving those peoples lives. I don't know if they all made it."

Mr Winston, a sergeant who served from 2006 to 2011, commandeered the vehicle after finding the set of keys inside the truck.

"I saw a field with a bunch of white trucks...I tested my luck to see if any had keys," he told CBS News.

"We started looking for people who needed taking to hospital, there was just too many and it was overwhelming how much blood was everywhere."

He told the injured to apply pressure to wounds as he attempted to speed to Desert Springs Hospital Centre "before they bled out".

He fears some of his passengers, who included a woman with neck and chest injuries, may have died.

"I can’t be for certain," he said. "There’s a few that I don’t think probably made it. They were pretty limp when we were pulling them out of the truck, but they still had a pulse, so I’m hoping for the best."

Mr Winston estimates he transported between 20 and 30 people to the hospital in multiple trips.

Las Vegas Sheriff Joseph Lombardo said on Wednesday the number injured in the attack was 489, and the death toll still stands at 58.