SANTA ANA, Calif. (AP) — Fred Rowbotham’s plan was to leave job stress behind with a trip to Las Vegas to celebrate his 45th birthday at the Route 91 Harvest country music festival.

But when the rat-a-tat-tat of gunfire rained down, the police officer from Chula Vista, California, sprang into action as if he were in uniform. Joining him were many other off-duty police and firefighters in the terrified crowd of 20,000.

“Cops and firefighters like country music. They like a good time. They like to go to Vegas and cut loose,” Rowbotham said. After rushing his wife to safety, he turned to help others. “You have to just act sometimes.”

The rampage by a heavily armed gunman perched in the nearby Mandalay Bay casino hotel killed 58 people and left nearly 500 injured, but it could have been deadlier without the quick thinking and tactical skills of officers who took charge, treated the wounded and directed paramedics to the most urgent victims.

Without their expertise, more people could have died, said Dr. Douglas Fraser, vice chief of trauma at University Medical Center of Southern Nevada, where many of the wounded were treated.

“It was very helpful to have people who were off-duty or medically trained there,” said Fraser, noting that a victim with a major injury to an artery can die in minutes. “It’s invaluable to be able to apply direct pressure to a wound or be able to place a tourniquet instead of watching someone bleed to death.”

Rowbotham said his instincts took over. He got pelted by shrapnel and was bleeding but unfazed as he directed dozens of people to safety.

Several other officers and firefighters were also hit, including Mike Kordich, a firefighter from Rancho Cucamonga, California.

He was giving CPR to a badly wounded person when he was struck in the arm by a bullet.

“I kept doing chest compressions with one arm until I noticed I was starting to bleed a lot,” Kordich recalled. He ran for cover, jumping fences, and said he could hear the bullets whizzing by.

San Diego police officer Tom McGrath said he threw himself on top of strangers to shield them. He treated the wounded, taking his shirt off to apply pressure to a woman’s bleeding chest. For another gunshot victim, he made a tourniquet from a scarf and tree branch.

“It was almost automatic to go from enjoying the concert to that person needs help,” McGrath told reporters Wednesday at San Diego police headquarters. “I think it’s something that just kind of gets ingrained in you. The switch flipped at that point.”

President Donald Trump visited Las Vegas on Wednesday and paid tribute to the first responders and doctors who rushed to save lives.

“While everyone else was crouching, police officers were standing up as targets just trying to direct people and tell them where to go,” Trump said. “Words cannot describe the bravery the whole world witnessed Sunday night.”

Bruce Ure, a deputy police chief from Seguin, Texas, shrugged off kudos and said he was just doing his job.

“I was ready to go. I knew it needed to be done because I had been trained in that,” said Ure, who spotted a man bleeding from a leg wound and dragged him to safety, then used the man’s belt to make a tourniquet.

Bullets were still raining down when he helped two other women, one shot in the back and one shot in the chest, by commandeering a vehicle and directing the driver to a nearby trauma center.

That night, Ure said, he saw America “at its finest and at its worst.”

Nearly four days after the shooting, many of the off-duty officers were back on the job and processing what they went through.

“I have been in combat, but I have never seen this type of mass casualty,” said police Sgt. Michael Gonzalez, who works in Santa Ana, California. He went to Las Vegas to teach a course on workplace violence but decided to check out the country music festival before going home.

One officer with him used a stethoscope as a tourniquet for a wounded woman, tightening it with a pen and tape, he said. Another cut strips of a first aid tent to use as tourniquets for other victims, he said.

“We go out into the street and start flagging down cars. Citizens are stopping. We put three, four, five in a truck, hit the truck — go!” he said. “And we go right back into the hot zone, (to) load two or three more.”

Gonzalez is back at work as a patrol sergeant but said he knows other officers so traumatized by the massacre they cannot return to duty yet.

Ure is one of them.

“I don’t know that you ever get over it,” he said by telephone. “I think you just try to figure out how to cope with it.”

[Featured image: Associated Press/Dennis Poroy, Nelvin C. Cepedia, Amy Taxin]