The report by the Federal Emergency Management Agency, the Clark County Fire Department and Las Vegas police provided an overview of first responders' actions on Oct. 1 and ways authorities can improve.
"It's almost impossible to jump hundreds of responders into an ongoing immediate event and have it go smoothly, communications wise," Fire Chief Greg Cassell said in an interview with The Associated Press.
Among more than 1,500 calls that police and fire dispatchers answered within the first two hours of the shooting were 16 false calls. They include reports of an unattended backpack at an emergency medical site, a hotel fire, and active shooters at casinos and the nearby airport. One report said 20 hostages were being held at the New York-New York resort.
"Congested radio traffic made coordination difficult for response agencies," the report said. "The calls caused a heightened sense of alert, and in some cases the fear of a multi-pronged, coordinated attack near the initial shooting."
It said fire dispatchers and firefighters were not even aware of the country music festival that 22,000 people were attending as Stephen Paddock opened fire from the windows on the 32nd-floor of the Mandalay Bay casino-resort into the outdoor concert below. He killed 58 people and injured more than 850 others before killing himself.
Police and an ambulance company were at the Route 91 Harvest Festival, but because the fire department was not part of the on-scene event command post, "command and control were fractured," the report said.
Medical supplies and an aid tent were "insufficient for a mass casualty incident of this scale," and there were "multiple altercations" with panicked and intoxicated concertgoers who wanted to help.
The report said that for special events of the festival's size, a "unified command post should be established among all agencies."
Cassell told reporters after the report was made public that a multi-agency program created after the terrorist attacks in Mumbai in 2008 allowed police, fire and emergency medical services to have a coordinated response to the mass shooting on the Las Vegas Strip. He said the department has moved to release the report faster than agencies in other communities that have seen mass shootings in an effort to share the lessons learned.
Cassell said the department has begun switching some of its phones to a system that is exclusively for first responders. The report highlighted that the overwhelming use of cell towers in the area led to sporadic, and at times, non-existent service to the department's mobile command computers.
"On that night, just as any night if you are at any large events, people need to use their cellphones at the same time to say 'We just scored a goal at the hockey game' or whatever, it really bugs down the system," he said. "So, that same thing (happened) that night. Twenty-thousand plus people were more than likely calling 911 in a very short time frame, and the system has a limit to what it can carry."
The report also said reflective vests that off-duty Las Vegas officers are required to wear while working at large events can make them a target for a shooter.
FEMA recommended officers be told to immediately remove the vests during an attack and that police should reconsider whether officers should wear them if they're not doing traffic control.
Cassell called the nearly 10-month review a first-of-its-kind effort uniting FEMA and local agencies after a large attack.
Earlier this month, Las Vegas police issued a final investigative report on the shooting, with no motive found. An FBI final report is expected by the end of the year.
The report released Monday found that incident commanders received constant updates about the number of officers ready to deploy from staging areas, and that police effectively diverted resources from other law enforcement agencies to hospitals and hotels after reports of other active shooters.
"We learned that a lot of things we've done since 2011 in operational readiness and plans has paid off," Cassell said. "Hopefully there is no next time."