He went to high school in the Los Angeles suburb of La Palma, where his mother still lives. Crystal Lancaster, who lives next door to the tan, stucco home, said it was "a big shock" to hear Dorner was the subject of a manhunt.
"We all couldn't believe it. We didn't know him that well, but he seemed like a really nice guy," she said.
While in high school, he played football and was part of the police explorer program, said another neighbor, City Councilman Gerard Goedhart.
He went to college at Southern Utah University, where he was a running back on the school's football team and graduated with a degree in political science in 2001, the school's athletic department spokesman Neil Gardner said.
"Chris Dorner is the last person I would ever think would do such," Gardner said Thursday. "He was a great kid."
Usera, his Southern Utah classmate, also had many kind words for Dorner, who he said was "smart and insightful" and "a perfectly rational human being." But he also conceded his old pal could be recalcitrant.
"He was a person of conviction and when he made up his mind about something, right, wrong or otherwise, he made up his mind and you weren't going to convince him otherwise," Usera said.
Though Usera received an "out-of-the-blue" phone call from Dorner four years ago complaining about conditions at the LAPD, he sensed nothing that would have foretold the mayhem that has unfolded in the last 10 days.
"Never anything that I experienced in a million years would lead me to conclude that this horrendous activity that he engaged in at this point was ever imminent or would ever be any type of concern," he added.
But if everything police say about Dorner is true, Usera said he isn't necessarily surprised.
"I think (his stubbornness) may be one of the things that brought about his demise in this case. I don't think once he got going on this, frankly, this mission of vengeance that he was on, based on his personality type -- the way I knew him -- there was not going to be any good end to it," Usera said.
After college, Dorner joined the Navy, receiving a commission as an ensign in July 2002. He trained in river warfare units and served a 2006-2007 stint in Iraq guarding oil platforms, according to Pentagon records.
He held a commission as a lieutenant until Feb. 1 and was rated as a rifle marksman and pistol expert, according to the records.
He also received several decorations, including the National Defense Medal, Iraq Campaign Medal, Global War on Terrorism Service Medal, Sea Service Deployment Medal and Navy Marine Corps Overseas Service Ribbon.
He enrolled in the LAPD Academy in February 2005 and spent four months on the streets as a trainee before being recalled to active duty for his stint in Iraq, police records state.
In Dorner's manifesto, he flatly blamed the LAPD for costing him his naval and law enforcement careers, but again doesn't elaborate, and says he has tried everything possible to restore his good name.
"I lost my position as a Commanding Officer of a Naval Security Forces reserve unit at NAS Fallon because of the LAPD," he wrote. "I've lost a relationship with my mother and sister because of the LAPD. I've lost a relationship with close friends because of the LAPD. In essence, I've lost everything because the LAPD took my name and new (sic) I was INNOCENT!!!"
He calls his rampage "my last resort," according to the manifesto.
Dorner writes that he knows that people who have been acquainted with him will be surprised by "media reports that I am suspected of committing such horrendous murders and have taken drastic and shocking actions in the last couple of days."
He goes on to even predict the nice things that would be said about them and assure the purveyors of those comments that he had no other choice.
"You are saying to yourself that this is completely out of character of the man you knew who always wore a smile wherever he was seen. I know I will be villified (sic) by the LAPD and the media. Unfortunately, this is a necessary evil that I do not enjoy but must partake and complete for substantial change to occur within the LAPD and reclaim my name."