UPDATE (10:30 a.m. PST) The mother of the man who killed nine people at Umpqua Community College two years ago told investigators he struggled with emotional problems since childhood, entertained himself by watching videos of killings online and amassed a collection of 13 guns with money made selling video games — and possibly money she gave him.

Douglas County officials announced Friday that they have completed their investigation into the Oct. 1, 2015, mass shooting — and that they will not file criminal charges against anyone.

Douglas County District Attorney’s letter stating no criminal charges to be filed in UCC shooting 

The shooter killed eight classmates, an assistant professor and, after police arrived, killed himself in an English class at the Roseburg school.

There had been questions about how the killer, a 26-year-old with a long history of psychiatric problems, obtained an arsenal of weapons. But the Douglas County District Attorney’s office said the investigation found the shooter acted alone and there was no cause to charge anyone else in the case.

The investigative reports released Friday largely confirm what witnesses and law enforcement said after the shootings: the killer entered his English class two years ago firing; he made his classmates lie on the floor; he chose his victims seemingly at random, though he did ask several what religion they practiced. It also confirms the killer, who also wounded nine people, left behind a manifesto seemingly explaining his actions.

He handed the manifesto, six typed pages stored on a thumb drive, to a student in the classroom during the shooting and told the student to deliver it to police. It’s a long, rambling diatribe, filled with racist commentary. In it, the shooter describes himself as “the most hated person in the world,” and says he belongs with “people who are elite.” His list of “people who stand with the gods,” include the killers at Columbine High School and Sandy Hook Elementary School.

A friend of the shooter’s told investigators that he was “very anti-Christian” and spoke of being molested by a man at church when he was young.

In an interview with investigators, the killer’s mother described a young man who had struggled to control his anger since early childhood and considered himself “superior” to other people his age. She told detectives he was “born angry pretty much” and received several, sometimes conflicting, diagnoses that might explain his inability to control his rage.   

She told them that at age 19 or 20 he once pointed a shotgun at her after she upset him. His mother told investigators she had been “anti-gun,” but that her son convinced her try shooting. They shot together at gun ranges in Roseburg and Eugene, she said.

The killer’s mother told police he’d never held a job. He bought guns — investigators found 13 that belonged to him — by selling his used video games. She said she also gave him money that he could have used to purchase weapons. His mother told investigators he “got entertainment from watching videos of killings on various websites.”

She also told investigators she believed her son planned the shootings “maybe not months or weeks in advance but at least days in advance.” She said her son was “not an impulsive person.” She speculated that perhaps he’d been set off by “a culmination of his frustration from his loneliness and anger.”

“Something triggered a bomb that was already there,” she’s quoted as telling investigators in their report.