It was four weeks until classes started last fall, so Chris Harper-Mercer logged into an online forum and whiled away an August morning. He was 26, unemployed, a second-time community college student on academic probation.

He marveled at how a stranger in Virginia shot and killed two people on live television and captivated the world. So many people like the gunman are all alone, Harper-Mercer noted five days after the on-air shooting.

"Yet when they spill a little blood, the whole world knows who they are."

One month later, on his second day of class, Harper-Mercer gathered five handguns, a rifle, extra ammunition and a steel-plated flak jacket.

He killed his professor and eight classmates, injured eight others and died after a shootout with police. The youngest victim, who survived, was 16. The oldest, the teacher, was 67. He was shot and killed first in front of his panicked students. Survivors remember the shooter ordering them to the floor and taunting them amid the terror.

The massacre at Umpqua Community College was the deadliest school shooting in Oregon history.

"Our lives are shattered beyond repair," the family of victim Quinn Cooper said in describing the act of a "deranged" shooter. "No one should ever have to feel the pain we are feeling."

Law enforcement officials have divulged almost nothing about the shooter in the five months since that day. Chris Harper-Mercer's mother has not responded to numerous interview requests. His father said in an email last month that he would not comment.

The Oregonian/OregonLive pieced together the few existing public records of Harper-Mercer, interviewed others who knew him, reviewed thousands of messages posted in online forums by his mother and scoured the digital traces that he left on social media.

Together, these elements provide a window into his mindset leading up to the massacre -- the final chapter of an aimless life, steeped in isolation and stoked by a passion for guns.

Note on the victims

Law enforcement officials initially said nine people were injured in the shooting, based on the number of survivors seen at area hospitals. Victims advocates now say eight were injured, while a ninth person was treated for shock but not physically harmed.

Federal agents have linked 14 firearms to the shooter, all obtained legally by himself or a family member. Authorities have not said whether the gunman had a mental health history that should have stalled these acquisitions. Prosecutors are still trying to determine if anyone should face criminal charges.

The sheriff leading the ongoing investigation vowed, early on, never to utter the gunman's name to deny him the recognition he craved. Some Americans believe that no part of a mass killer's biography bears repeating.

Yet knowing what preceded the Umpqua gunman's decision to open fire provides essential context amid the nation's quest to stop a seemingly endless stream of mass shootings.

An outsider

Christopher Sean Harper-Mercer had one constant in life. He grew up as the center of his mother's existence.

Harper-Mercer was born five months after his parents wed on Valentine's Day 1989. His mom and dad split before he turned one.

For two decades, he lived with his mother Laurel Harper on the eastern outskirts of the Los Angeles suburb of Torrance. The pair kept to themselves in their one-bedroom apartment. Neighbors rarely saw Harper-Mercer play with other children on the parking lot that doubled as a basketball court.

"They never opened the door, the windows, nothing," said a woman who lived next door for six years. The woman, whose native language is not English, asked not to be identified, because she didn't want to be linked to the Oregon shooter.

"When he got old, we just see him go downstairs with a backpack."

His mother was also a student. Her online resume shows she became a medical assistant and then returned to school to study nursing. She received her vocational nursing license in 2005.

As she studied, she and her son got by on welfare, scholarships and "family money bailing me out from time to time," she wrote online in 2009.

Money was always tight. Harper-Mercer's parents jointly filed for bankruptcy when he was 2. His father, Ian Mercer, went bankrupt again a decade later.

Harper-Mercer visited his father's trailer house in nearby Harbor City whenever his mom could ferry him the short distance there, said his half-sister, Anntionet Day. She was six years older and lived with their dad for a year as a teen.

She remembers her seven-year-old brother was happy and hyperactive. "He loved to dance to hip-hop and rap," she said.

What she recalls most clearly is how often Ian Mercer was gone. As the siblings grew up, they bonded over their shared anger toward their father.

Harper-Mercer's parents agreed to share legal custody when their divorce became final in 2006. By then, his dad had relocated an hour's drive north to Tarzana. Ian Mercer managed a suburban Noah's Bagels shop.

At Laurel Harper's urging, the siblings stayed in touch after their father moved away. They discussed life, psychology, religion and politics over long meals at Sizzler or Denny's, Day said. He considered what she had to say and seemed open to new ideas. She knew he was picked on and had a hard time making friends.

"He was an outsider," she said.

'No babbling idiot'

While Harper-Mercer struggled to fit in at school, at home his mother adored him and tracked his every move. She shared glimpses of their life with her adopted Internet community.

Laurel Harper dispensed reams of advice on Yahoo Answers, an Internet forum where people pose questions. She weighed in more than 33,900 times over the course of nearly nine years, plus hundreds more times elsewhere on the Internet. She usually used the pseudonym "TweetyBird."

She wrote that her son was diagnosed with Asperger's Syndrome as a child, and that she had Asperger's as well. Doctors no longer distinguish Asperger's from autism, a neurobiological disorder that can make social interaction and communication difficult, leading to a sense of isolation.

One struggle that young adults with autism face is navigating adulthood after support systems, well developed for school-age children with special needs, come to an end. A years-long survey showed that in young adulthood, people with autism live on their own far less often than peers with other disabilities, according to the A.J. Drexel Autism Institute.

Harper said she had taught her son social cues by miming, something she called the "gesture effect." She was proud of him.

"He's no babbling idiot nor is his life worthless," she wrote online in 2007. "He's very intelligent and is working on a career in filmmaking."

As a teen he attended Switzer Learning Center, a nonprofit special-education school near his home. The school works with students from third grade through young adulthood, offering job training and life skills. Officials would not say how long Harper-Mercer was enrolled.

It's unclear whether Harper-Mercer received such focused support after high school.

The local newspaper announced his graduation from Switzer in June 2009.

Shared hobby

Christopher Harper-Mercer

As they contemplated his future, the teen and his mother both developed a zeal for firearms.

In one photo on Myspace, Harper-Mercer tilts his head toward his right shoulder and props a gun barrel against his left. His thick black glasses cast shadows on his cheeks.

Other pictures promote the Irish Republican Army, the outlawed paramilitary group committed to ending British rule over Northern Ireland. Harper-Mercer called them "freedom fighters" and pointed out the types of guns they held.

Neighbors often saw him wearing camouflage and combat boots.

His mother amassed a cache of guns. In several separate posts, she described owning eight firearms, including three types of pistols, a 12-gauge shotgun and a high-velocity rifle.

Her writings suggest self-protection may be one motivating factor. The Oregonian/OregonLive found no record that she or her son ever reported being crime victims. Police in Torrance had no reports of interacting with the pair, though records involving minors are sealed.

"I keep all my mags full," Harper wrote online in 2012.

"I keep two full mags in my Glock case. And the ARs & AKs all have loaded mags. No one will be 'dropping' by my house uninvited without acknowledgement."

A struggle for independence

Christopher Harper-Mercer attended El Camino College in his hometown of Torrance, California for five semesters, but never graduated. The campus is shown here in December 2015.

Harper-Mercer foundered as he entered young adulthood.

He enlisted in the Army in November 2008 to become a combat engineer, a soldier who works on war zone construction projects. He shipped to Ft. Jackson outside Columbia, South Carolina, as the U.S. planned to send thousands more troops to Afghanistan.

He hadn't finished high school, so the Army sent him to a novel preparatory program to help recruits obtain GEDs. He lasted five weeks.

A spokesman said the Army discharged Harper-Mercer in December 2008 "for having failed to meet enlistment medical/physical requirements." The Army did not provide specifics.

Harper-Mercer's career path never regained definition. He started taking classes at the local El Camino College in 2010. And for two years, he succeeded. He aced history and political science, earned a B in basic arithmetic and maintained a 3.3 GPA.

But his grades plummeted during his fifth and final term in the spring of 2012, college transcripts show. His mother left her long-time job that March and took on work as a home-hospice nurse, according to her resume.

Months after he quit college, his mother lashed out online at another parent who she believed was providing a crutch for an alcoholic adult son.

"Let him stand on his own feet, or fall, and let him face the consequences of his decisions and actions," she wrote three weeks before her own son turned 23. "You're preventing this."

Harper-Mercer had fallen out of touch with his sister three years earlier, after her wedding. Life, she said, got busy.

He turned to the Internet for friends, seeking pen pals and dates under the name "ironcross45." He used the moniker on a dating website called Spiritual Passions, where he posted a photo of himself wearing a necklace and a gray muscle shirt. He joined groups for people who enjoy meditation and the occult, but not organized religion.

He said he wanted "someone who shares my beliefs, and is similar to me."

An unknown in Oregon

Harper-Mercer spent the final years of his life, like all the others, dependent on his mom. What changed was that the pair were in a totally new environment: Southern Oregon.

The dot-on-the-map town of Winchester hardly noticed when they arrived in February 2013. They had decided to move to the area the proceeding fall, when Laurel Harper obtained a nursing license in Oregon.

The mother was the first to establish a connection with Umpqua Community College. The rural school is named after the river that flows between the campus and the Harpers' apartment complex just north of Roseburg. The school opened in 1964 and educates more than 2,000 students every year. Most come from the timber towns of Douglas County.

Laurel Harper started classes at Umpqua within months of moving nearby to further her nursing career. She stayed for seven semesters. She also worked as a home nurse, said Jesse Steele, who hired her to care for his son in nearby Winston. Steele said Harper was a loner who did not associate with many people outside work.

Harper-Mercer applied three times to enter the school his mother attended. At first, he intended to pursue an associate degree in computer information systems. He later switched his major to general education, according to college records.

But two years passed before he ever registered for classes.

In the meantime, he kept to himself. He obtained a driver's license in 2013, the same year that his mother wrote about buying him a Jeep Liberty. He registered to vote as an independent and voted in two elections.

Neighbors in the apartment complex saw a gun holstered to his hip when he took out the trash and retrieved the mail.

On one unseasonably warm Sunday in March 2014, he made his way to a park a half-mile from his apartment. He walked onto a rusted railroad bridge that crossed the North Umpqua River and wandered until a Douglas County sheriff's deputy stopped him on the narrow platform.

The entire encounter between the deputy and Harper-Mercer was so perfunctory that the subsequent report misidentifies his race as Hispanic. His mother is African-American, his father is a white British immigrant.

It was the first and the last time officers noted his existence.

The last summer

The balcony of the Winchester, Oregon, apartment where Chris Harper-Mercer moved with his mother Laurel Harper in February 2013.

Harper-Mercer finally decided to enroll at Umpqua in early 2015, eight months before the mass shooting. What might have been a route to independence quickly went off course.

During his first semester, he helped build sets for the spring play and stayed out of the spotlight. A photo of the cast and crew doesn't show him. But his top mark in the single-credit theater course couldn't offset the C he earned in personal finance. His grades fell further during the summer semester when he got a D in business.

He landed on academic probation, and college officials told him to lift his grades. They sent Harper-Mercer a form letter that encouraged him to meet with academic advisers. It's unclear if he ever did.

Apart from class, he filled his summer days on the computer, publishing his personal views on topics such as materialism.

Looking back on Harper-Mercer's writings, his sister says she recognizes a sense of alienation. Her biggest regret is not reaching out.

"At 26, you're still going through a lot," she said.

"He was lonely. I really wish I had known."

No clinical view of Harper-Mercer's psychological state at the time is available. Authorities have declined to disclose his mental health history.

He posted online that summer under the name "lithium_love." Doctors usually prescribe lithium, an antipsychotic drug, to treat bipolar disorder.

In his online world, Harper-Mercer noted one path to renown. He wrote on Aug. 31, five days after gunman Vester Flanagan fatally shot two people in Virginia:

"Seems the more people you kill, the more you're in the limelight."

If Harper-Mercer's mom detected changes in her son's condition, she did not share her concern widely. She held to her optimistic outlook and devoted much of September to creating upbeat YouTube tribute videos. She uploaded her final one, a four-minute motivational montage set to "Don't Stop Believin'" on Sept. 28.

"Dreams come true," she captioned the video, "and when they're set to this great Journey tune, they're sure to happen!!"

The next day, Harper-Mercer left the apartment he shared with his mother to start a third term of classes. The director of the coming school play, a British comedy called "Blithe Spirit," chose him to be a production assistant.

For the first time in his Umpqua career, he attended a course in a classroom rather than online or backstage. The class was Introduction to Expository Writing. He returned on Thursday carrying a handgun.

He singled out one victim, then another, and another. One woman, ordered to stand, instead kept still beneath a dying classmate. The shooter deemed another student "the lucky one" who would deliver a digital manifesto to police. Both survived to recount what happened in Snyder Hall.

As families reeled from the senseless horror, Douglas County Sheriff John Hanlin told them "our hearts will be with you forever."

"Please know that we consider your loved ones our heroes," Hanlin said. "They will never be forgotten.''

Jeff Manning of The Oregonian/OregonLive contributed to this report.

-- Molly Young

myoung@oregonian.com

503-412-7056

@mollykyoung