The gunman who killed nine people at an Oregon community college was armed with three pistols and a rifle, as well as five additional magazines, authorities said.
Chris Harper-Mercer, whose father is reportedly English, opened fire at Umpqua Community College in Oregon on Thursday before dying in a shoot-out with police.
The shooting at Umpqua Community College also wounded seven.
The details of his weapons arsenal emerged as Oregon governor Kate Brown urged that the debates over America's gun laws wait, to allow the community to support grieving families.
Authorities investigating the massacre said they had found a number of firearms at the 26-year-old's apartment, as well as a cache he had on him as he carried out the killings.
Harper-Mercer had a 9mm Glock pistol and .40-calibre Smith & Wesson on him when he opened fire at the college, authorities said.
He also had a .556-calibre Del-Ton rifle and a .40-calibre Taurus pistol, which was traced to someone in Portland, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).
Six weapons were recovered from the community college, including a rifle, along with a steel-plated flak jacket.
Federal investigators who searched his home also found seven weapons there.
ATF assistant special agent in charge Celinez Nunez said that all of the weapons were purchased legally, seven of them by the shooter or his family members in the last three years.
Harper-Mercer is not believed to have had a criminal history. Investigators believe he may have been a student at the college because a receipt found at the scene showed he purchased textbooks from the campus bookshop two days before the shooting.
It has emerged that Harper-Mercer also failed basic training for the US Army in 2008.
Calling for action to prevent further "senseless violence", Ms Brown said: "Oregon has worked continuously to prevent these kind of tragedies. But they continue to happen here and across the nation and they are going to keep happening until we decide we want them to stop.
"There is no single solution that will prevent every shooting but we must and we will do better to prevent this senseless violence.
"This is a conversation we will have but today is not the day."
US senator Ron Wyden, Oregon's senior senator, added that Oregon was the "right place to lead the conversation". He said: "As a country we cannot just shrug our shoulders and move on."
Harper-Mercer's family have spoken of their shock over the incident.
His father, Ian Mercer, told reporters he was "just as shocked as everybody else" at his son's actions.
The killer, whose social media profiles featured content supporting the IRA, apparently demanded to know his victims' religious beliefs before opening fire at the campus in Roseburg, Oregon.
Speaking with a distinctive English accent from his home in the US, Mr Mercer told reporters: "I've just been talking to the police and the FBI and all the details I have right now is what you guys (reporters) have already.
"I can't answer any questions right now, I don't want to answer any questions right now.
"It's been a devastating day, devastating for me and my family.
"Shocked is all I can say."
Carmen Nesnick, Harper-Mercer's step-sister, said he was born in the United Kingdom and travelled to the United States as a young boy.
She added: "I'm actually still shaking and my mom is in there crying. I don't know what to do."
Several people remain in hospital following the incident, the 45th school shooting in the US this year.
Authorities initially refused to name the gunman, and shed no light on his motive.
Witnesses described the moment Harper-Mercer stormed the school.
Kortney Moore, 18, said she was in a writing class when a shot came through the window and hit the teacher in the head.
The gunman then entered the Snyder Hall classroom and told people to get on the floor, she told the Roseburg News-Review newspaper. He told people to stand up and state their religion before opening fire.
The gunfire, shortly after 10.30am local time, sparked panic as students ran for safety and police and ambulances rushed to the scene.
Hannah Miles, 19, said she was in her writing class when her teacher got a call from security saying the school was in lockdown. She heard gunshots from a neighbouring classroom.
She said that, huddled together in the locked classroom, the students and teacher heard footsteps outside and a man's voice call out to them: "Come on out, come on out." They remained quiet and did not open the door.
Police soon arrived and, after students were convinced that they were indeed officers, they opened the door.
"It was like a huge burden had been lifted," she said. "A huge sigh of relief that we were going to be OK."