People pay tribute to victims after the mass shooting during a music festival in Las Vegas last year. (Salwan Georges/The Washington Post)

Las Vegas police officers who rushed last year to the scene of the deadliest mass shooting in modern U.S. history encountered horror and chaos, describing later how an otherwise routine night for so many quickly gave way to terror.

“It started just like any other shift,” one officer wrote in a police report, among scores of such records made public Wednesday.

Then the warnings about an active shooter began to blare from police radios, the officer wrote, followed by the sounds of automatic gunfire.

During the Oct. 1, 2017, massacre on the Las Vegas Strip, a gunman firing from a high-rise hotel killed 58 people and injured more than 850 others. During the initial gunfire, police wrote in their statements, many at the country music festival were unsure what they were hearing, while officers who responded were not clear where the threat was coming from.

Officers described hearing “the sound of bullets whizzing by our patrol vehicle,” and one said they took cover but had to leave it during the volleys of gunfire to keep people fleeing the concert venue “from inadvertently running back into the line of fire.”

When police responded, officers later wrote, it was not certain where the shooter was — or if there were multiple attackers. The police reports showed the confusion that spreads during such frantic, terrifying scenes, as well as the stunned realization about what was unfolding.

“It sounded like fully automatic fire,” one officer wrote in a police report, “and we were in disbelief that it could be what we were thinking.”

These accounts were included in about 2,000 pages of statements, witness interviews and other documents released Wednesday by the Las Vegas police. These records shed further light on the havoc that unfolded when a lone gunman perched at the Mandalay Bay Resort and Casino fired upon a crowd at the Route 91 Harvest music festival.

Police said the gunman, Stephen Paddock, fired at the crowd below for more than 10 minutes before turning one of his guns on himself. Authorities have said they still do not know what motivated the attack.

Among the records released Thursday were some from officers who spoke to people who knew Paddock and described him as an angry gambling addict and a loner. Police also released statements from witnesses to the shooting and one from a person who claimed to have given a haircut to a man with the last name “Paddock” who, in June, had remarked that outdoor locations in Las Vegas could be targeted by people firing from nearby casinos.

These accounts and police statements were the latest wave of records made public by the police after media organizations, including The Washington Post, went to court to force their disclosure. Police had initially refused, citing the ongoing investigation, but a judge sided with the media outlets.

Police first released video footage captured on the body cameras of officers who went to the gunman’s suite. Last week, police released accounts from people who survived the massacre, including some who were shot while trying to flee or saw others gunned down in front of them. That release also included statements from hotel employees who had encountered Paddock and found him unremarkable, saying he set off no red flags.

Witness accounts had described the violence and uncertainty that unfolded during the shooting, with people unsure where to run or how many shooters were opening fire. The police statements similarly touch on the mayhem that often reigns during and after mass shootings.

Some police officers, like others at the concert, initially mistook the gunfire for fireworks. A police officer who gave a statement said they were at the show with their husband and “initially assessed the noises to be fireworks, or a speaker malfunction.” More volleys increasingly made it clear they were hearing gunfire, the officer wrote.

Information was scarce as police went to the scene. A detective recalled heading to the venue knowing only that there was a shooting with a “large number of casualties.” The detective and another officer went to look for any injured victims or people who were hiding, moving behind a shield that provided “minimal” cover as they searched, the detective wrote in a statement after the shooting.

They found 17 victims, but all 17 were dead, the detective wrote. Eventually, they found people who were hiding and were able to help get them to the exit.

Some officers were already working that night — including at the festival targeted by the gunman — while others were at home when the calls began to come in.

Other officers said they were called with warnings about additional shooters opening fire at the Mandalay Bay or elsewhere on the Las Vegas Strip. Reports of multiple shooters are frequent during such attacks, though there are rarely additional attackers.

One officer wrote of being warned about potentially as many as three shooters inside the Mandalay Bay. The officer “assumed they were randomly roaming the casino.”

Another officer went to the New York-New York Hotel & Casino in response to a report of another active shooter, but found nothing. Then the officer went to the Bellagio, and then the Tropicana, both for active shooter calls that were untrue. Another call came in about a man with a rifle going into Caesars Palace, the officer wrote. When police went to check, they found that this man was the vice president of security.

Further reading:

The lives lost in Las Vegas

‘I’m constantly asking: Why?’ When mass shootings end, the painful wait for answers begins.

‘The club no one wants to join.’ Mass shooting survivors find solace in one another.

Red flags. Warnings. Cries for help. How a system built to stop the Parkland school shooter repeatedly broke down