The gunman who went on a deadly rampage at an Oregon college in the US was well armed and equipped with extra ammunition, authorities said on Friday, and he may have killed more people if not for the heroism of a military veteran in an adjoining classroom.

A day after the shooter killed nine people and wounded nine others at Umpqua Community College in Roseburg, authorities sought a motive for this year's bloodiest mass shooting in the United States, where such massacres have become all too common.

The gunman, who was killed by police, had 13 weapons, body armor and ammunition, said Celinez Nunez, assistant special agent of the US Bureau of Alcohol, Tobacco, Firearms and Explosives.

He burst into a classroom in the former timber town, about 180 miles (290 km) south of Portland, shot a professor in the head and then ordered cowering students to stand up and state their religion before shooting them one by one, according to survivors' accounts.

As the gunman moved toward an adjoining classroom, Chris Mintz, 30, a US Army combat veteran who served in Iraq, tried to stop him, Jamie Skinner, the mother of Mintz's 6-year-old son told Reuters. The gunman opened fire, striking Mintz.

"When Chris hit the ground, he told him it was our son's birthday yesterday. He took a couple more rounds after that," said Skinner. The gunman then changed direction, entering a different room.

"The assailant was not able to make it into the classroom, because Chris stopped him," she said, noting Mintz is hospitalized with two broken legs and seven bullet wounds.

The Oregon shooting, the latest in a series of high-profile mass killings across the country, has led to fresh demands for stricter gun control in the United States, including an impassioned plea by President Barack Obama for political action, and statements by some Republican presidential candidates supporting the right of Americans to bear arms.

The latter is a position championed in the past by Douglas County Sheriff John Hanlin, who has repeatedly declined to name the gunman during press conferences since the shooting and refused to comment on the gun control issue.

Law enforcement sources have identified the suspect as Chris Harper-Mercer, 26.

"Media and community members who publicize his name will only glorify his horrific actions," he said. "And eventually, this will only serve to inspire future shooters."

Six of his guns were found on campus and another seven guns - all legally purchased - and a significant amount of ammunition were found at the apartment he shared with his mother in nearby Winchester, the ATF's Nunez said.

Although authorities have disclosed scant information about the gunman, they appeared to be learning more about him and why he might have opened fire.

The shooter left behind a "multipage, hated-filled" statement in the classroom, according to a tweet from an NBC reporter, citing multiple law enforcement sources who were not identified. CNN, citing sources, said the statement showed animosity toward blacks.

Hanlin declined to comment when asked about the writings at a press conference.

Harper-Mercer was born in the United Kingdom and arrived in the United States as a young boy, his stepsister Carmen Nesnick told CBS Los Angeles.

His parents, Ian Mercer and Laurel Harper, divorced in Los Angeles in 2006 when he was a teenager, according to public records, and he continued to live with his mother.

Harper-Mercer, who identified himself on a blog post as "mixed race," enlisted in the US Army and served for about a month in 2008 before being discharged for failing to meet administrative standards, military records showed.

He graduated from the Switzer Learning Center in Torrance, California, in 2009, according to a graduation listing in the Daily Breeze newspaper. Switzer is a private, nonprofit school geared for special education students with a range of issues from learning disabilities, health problems and autism or Asperger Syndrome, according to the school's website.

At some point, Harper-Mercer appears to have been sympathetic to the Irish Republican Army, a militant group that waged a violent campaign to drive the British from Northern Ireland. On an undated Myspace page, he posted photos of masked IRA gunmen carrying assault rifles.

GUN CONTROL DEBATE

Not counting Thursday's incident, 293 US mass shootings have been reported this year, according to the Mass Shooting Tracker website, a crowd-sourced database kept by anti-gun activists that logs events in which four or more people are shot.

Hours after Thursday's shooting, a visibly frustrated Obama urged Americans to press their elected leaders to enact tougher firearms safety laws.

"Somehow this has become routine. The reporting is routine. My response here, at this podium, ends up being routine," he said. "We've become numb to this."

Gun control advocates say easy access to firearms is a major factor in the shooting epidemic, while the National Rifle Association and other pro-gun advocates say the Second Amendment of the US Constitution guarantees Americans the right to bear arms.

Oregon Governor Kate Brown on Friday declined any comment on gun control or other ways of preventing future shootings.

"It is going to keep happening until we decide that we want them to stop," she said. "There is no single solution that will prevent every shooting but we must and we will do better."

Both the governor and the sheriff said the gun control conversation would have wait for another day and instead it was time to focus on providing the support and condolences to help the community heal.

A month after the December 2012 mass shooting at Sandy Hook Elementary School in Connecticut, Hanlin wrote a sharply worded letter to Vice President Joe Biden saying he would never enforce a federal law that violates the Constitution.

"Gun control is NOT the answer to preventing heinous crimes like school shootings," Hanlin wrote in the letter, dated Jan. 15, 2013. – Reuters