The cause of death of the gunman who killed nine people in the Oregon college massacre was suicide, according to the medical examiner. (Reuters)

Three police officers arrived at the scene of Thursday’s massacre at Umpqua Community College within six minutes of the first emergency call, exchanged gunfire with shooter Chris Harper Mercer and prevented him from “killing dozens of other people who were in that classroom and in the immediate vicinity,” Douglas County Sheriff John Hanlin said Saturday.

During the gunfight, Mercer, 26, killed himself, according to the state medical examiner. The information was released by Hanlin at Saturday’s final news conference on the mass shooting, which took the lives of 10 people, including Mercer, and injured nine others.

Hanlin also revealed that authorities had found another handgun belonging to Mercer, bringing his stockpile to 14. Authorities previously said he brought six of those weapons — five handguns and a rifle — to the school, along with a steel-paneled flak jacket and five extra magazines of ammunition. Hanlin also confirmed that Mercer was a student at the college and was registered for the class where the shooting started.

The new details were provided as police posted a statement from Mercer’s family that was released by a spokesman.

“We are shocked and deeply saddened by the horrific events that unfolded on Thursday, October 1,” the one-paragraph statement reads. “Our thoughts, our hearts and our prayers go out to all of the families of those who died and were injured.”

‘Our lives are shattered beyond repair’: The victims of the Oregon college shooting

Mercer’s father, Ian Mercer, who lives in Los Angeles, said he first learned that something was amiss when an FBI agent called him at work. During their meeting in person, the agent told Mercer his son was the shooter.

“It was unreal, pretty much,” Mercer said. “Just disbelief. You know, the FBI is not going to tell you something that is not true. It’s not likely anyway. So it was shocking, stunning, disbelief — you can name a thousand different emotions.”

In a lengthy interview with CNN on Saturday, Mercer said he was “trying to understand how [the shooting] can happen. . . . I’m at a loss for words right now.”

Clearly shaken, Mercer wondered how his son could have amassed his arsenal. “How is it so easy to get all these guns?” he said. “How is it so easy? . . . It has to change. How can it not?”

Douglas County Fire District Chief Greg Marlar said he was among the first to arrive at the school after the shooting. The first call had reported that an “active shooter” on the campus had left a single female victim gravely wounded.

Within seconds of his arrival, Marlar said Saturday, he found that a much more horrendous scene awaited. His firefighters and EMTs had trained at the school, but nothing prepared them for what he saw: Young women bleeding from bullet wounds walking toward them, begging for help.

“You’re always thinking it can happen somewhere else and not happen here,” Marlar said. “But it did.”

In classrooms, he said, gun victims littered the floor. Some were alive and bleeding, and more appeared dead or dying, including the shooter, who was handcuffed on the floor. “It was a horrific scene,” Marlar said. “I didn’t have time to think. We had a job to do.”

Marlar scanned the room and left after a few seconds. He stepped out to begin directing more first responders to the campus. A total of 45 emergency medical technicians and firefighters and 10 ambulances answered the call. “There is no doubt that the exceptional patient care and proficient use of lifesaving skills by first responders saved lives that day,” Marlar said.

They transported 10 wounded to area hospitals, but one person died on the way. For a short time the EMTs administered to Mercer, placing him on a gurney, Marlar said. But after they realized he had died, they put him back on the floor.

Later that evening, Marlar learned that one of the students who died, Treven Anspach, was the son of one of his firefighters, Justin Anspach. Marlar’s youngest son and Treven Anspach knew each other in high school, which made Marlar’s duties more difficult when, at 7 p.m. Thursday, he had to knock on the door of the Anspach family’s home.

“Nothing can completely prepare you for the physical and mental toll an incident can have on any responder,” Marlar said. “I haven’t stopped thinking about the many other families that have experienced an unthinkable loss.”

Donald Trump weighed in on the massacre during a suburban Nashville rally, suggesting Saturday that having more guns in the classroom might have saved lives.

“If you had a teacher or somebody with guns in that room, you would’ve been a hell of a lot better off,” the Republican presidential front-runner told a raucous crowd in Franklin, Tenn. Speaking later to reporters, Trump dismissed President Obama’s call for tougher national gun laws as “divisive,” and he criticized a Friday remark by former Florida governor Jeb Bush.

“He used the words ‘stuff happens,’ and I thought it was a very bad phrase to use,” Trump said of Bush.

A timeline of events distributed at Saturday’s news conference showed that the first 911 call from the college came in to the Douglas County Emergency Communications Center at 10:38 a.m. Roseburg police officers were dispatched to the school, about five miles from their location.

Two of them and a state trooper arrived at 10:44. At 10:46, one officer reported an exchange of gunfire with Mercer. The 10:48 entry says simply “Suspect down.”

Hanlin said the state medical examiner had determined that the cause of death was suicide.

At 10:50, the dispatcher requested that all local ambulances head to the school as authorities began to understand the magnitude of the carnage there. By 11:14, Mercy Medical Center was told there were 10 fatalities and six critically wounded patients who would be coming in.

At the news conference, Hanlin thanked the officers who stopped Mercer, as well as Chris Mintz, an Army veteran who survived seven shots to his back, legs, hand and other parts of his body as he tried to block Mercer from blasting his way through a classroom door.

And Hanlin spoke directly to families of Mercer’s victims, telling them that “we consider your loved ones to be our heroes. They will never be forgotten.”

Bernstein reported from Washington. Philip Rucker in Franklin, Tenn., and Rob Kuznia in Los Angeles contributed to this report.