LAS VEGAS (WASHINGTON POST) - Firefighter Joe Geeb did not know if there was one shooter, or 30.

When the call about a "mass casualty incident" blasted through the radio on Sunday (Oct 1) night, the Clark County fire captain had no idea what was happening on the Las Vegas Strip, but he immediately began thinking about how he would run towards the bullets, the mayhem and the carnage while everyone else was running away.

He quickly donned his flack vest and helmet designed to withstand rifle fire and gunshots. Then he paused as a group of armed police officers created a protective bubble around him and other firefighters.

Moving as one, the team hurled itself into the centre of the chaos.

"I knew the officers had my back and I would have had theirs," Captain Geeb said. "We're going to go in together and we're going to come out together."

Relationships between the nation's police and fire departments can range from friendly rivalries to downright acrimony.

In Las Vegas, officials are confident that an innovative effort requiring both agencies to train together to respond to active-shooter incidents saved countless lives in the massacre that left 58 dead.

Fire departments traditionally have waited on the sidelines of shooting scenes until police declare it safe for medics to go in and treat victims. In some cases, including high-profile mass shootings, that resulted in wounded patients bleeding to death even though medics could have saved them with immediate aid.

Learning lessons from the shootings at Columbine High School outside Denver in 1999 and at a movie theatre in Aurora, Colorado, in 2012, Nevada's first responders decided they should work while under fire.

"We saw from the reports of how these people died and the lack of interaction with the police departments and we knew we had to fix that," Clark County Fire Chief Greg Cassell said on Thursday.

Chief Cassell said police and fire agencies in Nevada have been working together since 2010 to develop concerted responses to critical incidents, but Sunday was the first time their years of training and drills deploying "rescue task forces" played out in real life.

Sixteen such task forces raced into the concert venue the night gunman Stephen Paddock opened fire from the 32nd floor of the Mandalay Bay Resort and Casino, sending volleys of bullets down on a country music festival full of 22,000 attendees, fire officials said.

Each task force included four to six armed police officers, who created a perimeter around three paramedics, said deputy chief of Clark County fire operations Roy Session, who deployed the teams throughout the night.

The medics treated and transported the wounded to ambulances under the blanket of safety those officers provided, moving in unison with police from patient to patient.

"What we discovered in Columbine and Aurora is that people were laying and dying waiting for help," Deputy Chief Session said. "This team was trying to avoid that."

The fire department has trained with police on skills including kicking down doors and treating patents in simulated live-fire environments, with blank rounds fired to ensure medics learn to do their lifesaving work while disrupted by the sound of gunfire.

Sergeant Branden Clarkson, of the Las Vegas Metropolitan Police Department, was one of the many officers who stood shoulder to shoulder with firefighters at a Clark County fire department news conference on Thursday to discuss Sunday's rescue efforts.

A decade ago, officials said, it would have been unusual to have even a single police officer at a fire department event."We have a joking relationship and a friendly rivalry, but when it comes down to it, we know we are there for each other," said Sergeant Clarkson, who heads the police department's efforts related to "multi-assault counter-terrorism action capabilities".

Firefighters and medics faced several challenges on Sunday as they responded to what they would later learn was the deadliest mass shooting in modern US history, Chief Cassell said.

People with gunshot wounds appeared at various hotels, but the calls were dispatched to first responders as a report of a shooter at each hotel. The calls initially generated more than 30 different possible shootings along the Las Vegas Strip. "That complicated our response," Chief Cassell said.

People scattered into hotels, to the tarmac of the airport and into neighbourhoods, creating a response area that stretched about a mile."It was not in one building, it was not in one spot, it was not in one address," Chief Cassell said. "It was spread over a massive area."

The fire department transported more than 200 people to area hospitals that night and treated victims suffering from gunshot wounds, fractures and trampling injuries from the stampede to escape the gunfire.

Some of the injured were wounded further as they were transported out. In some cases, those escaping loaded the most-injured person in a group into a truck or car first because the individual could not move. But then other people would pile on top of that person to get out of the area.

Captain Geeb and his team at one point helped 10 people who had crammed into a compact car. "Then there was the emotional chaos," said Captain Geeb, whose team treated dozens of people on Sunday. No firefighter or medic was struck by gunfire or injured, except one who hurt his knee in a fall.

Deputy Chief Session said the response to Sunday's shooting was built on lessons learnt from previous incidents, but training has focused on a shooter who is at ground level, not someone firing from an elevated position.

He said the department is already breaking down its response to Sunday's shooting to determine how to adjust for the future."Our goal is to learn from those lessons," he said. "Hopefully, we won't have to use this again."

Chief Cassell said that since Sunday's shooting, law enforcement agencies and emergency officials from all over the world have contacted him to commend him on the department's response and to ask for advice on how they can emulate it in the case of a similar incident.

Although Sunday's shooting was nothing anyone could have ever planned for, Chief Cassell said, it was something police and fire were ready to handle. It all came down to preparation and relationships."We love our cops, and they love us," he said. "That paid off for us the other night."