The gunman who killed nine people at an Oregon community college had body armor and was armed with six guns and five additional magazines, officials said.
ATF Assistant Special Agent in Charge Celine Nunez said six weapons were recovered at Umpqua Community College and an additional seven were found at the shooter's home.
All 13 firearms were purchased legally by the shooter or a family member in the last three years, Nunez said.
Investigators also found a flak jacket next to a rifle at the school, which contained steel plates, she said.
"This is a hunting state and firearms are common in most households," Douglas County Sheriff John Hanlin said at a press conference Friday, responding to the substantial number of weapons Mercer owned.
Hanlin said the medical examiner's office will officially release the shooter's name some time Friday, adding that no one from his department will use his name because “it will only glorify his horrific actions and will only serve to inspire future shooters."
The gunman, identified as 26-year-old Chris Harper Mercer, had a 9mm Glock pistol and .40-caliber Smith & Wesson, according to a Bureau of Alcohol, Tobacco, Firearms and Explosives incident report obtained by The Associated Press.
Mercer also had a .40-caliber Taurus pistol traced to someone in Portland and a .556-caliber Del-Ton.
The shooting Thursday at Umpqua Community College in Roseburg, a former timber town 180 miles south of Portland, also wounded seven people. Mercer died after a shootout with police.
Mercer isn't believed to have a criminal history. Investigators believe he may have been a student there because a receipt found at the scene showed he purchased textbooks from the campus bookstore two days before the shooting.
Law enforcement officials told NBC News that Mercer left behind a multi-page document at the shooting scene espousing what one of them called "a philosophy of hate."
Two officials familiar with the contents say he wrote that he would be "welcomed in Hell and embraced by the devil."
The officials said he lamented the fact that he had no girlfriend. "He said he had no life," another official said, adding, "He felt the world was against him."
Mercer had enlisted in the U.S. Army and was stationed at Fort Jackson in South Carolina from Nov. 5 to Dec. 11, 2008, before being discharged for "failing to meet the minimum administrative standards to serve, Army officials said.
The worst mass shooting in recent Oregon history was raising questions about security at the college with about 3,000 students.
"I suspect this is going to start a discussion across the country about how community colleges prepare themselves for events like this," former college president Joe Olson said.
Oregon Gov. Kate Brown said Friday we must do more to prevent mass shooting around the country, but added that talk of gun policies should wait until after the victim’s families had time to grieve.
“This is a conversation we will have but today is not the day,” Brown said.
Senator Ron Wyden echoed Brown's comments, adding "it is clear that it does have to be about more than words if we want this carnage to end."
Roseburg is in Douglas County, a politically conservative region west of the Cascade Range where people like to hunt and fish.
Sheriff Hanlin has been vocal in opposing state and federal gun-control legislation. In 2013, Hanlin sent a letter to Vice President Joe Biden after the shooting at a Newtown, Connecticut, elementary school, declaring that he and his deputies would refuse to enforce new gun-control restrictions "offending the constitutional rights of my citizens."
The Associated Press contributed to this story.