Rodger passed the background check needed to buy the firearm used in the shooting, a law enforcement official briefed on the investigation told CNN. The official said nothing had been found in the gun trace to indicate Rodger should have been disqualified.

Law enforcement officers were searching the separate homes of the suspect's mother and father Sunday, a law enforcement official with knowledge of the investigation told CNN. The officers were from the Santa Barbara County Sheriff's Department and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, the source said.

The manifesto

In the manuscript of his life's story, Rodger often mentioned feeling slighted or inferior, such as when he was denied entry on an amusement park ride at age 6 while other boys his age got to go on.

"Being denied entry on a simple amusement park ride due to my height may seem like only a small injustice, but it was big for me at time," Rodger wrote. "Little did I know, this injustice was very small indeed compared to all the things I'll be denied in the future because of my height."

He described his parents' divorce as a devastating, "life-changing event," but said he gained more respect for his father after he quickly acquired a girlfriend.

"Males who can easily find female mates garner more respect from their fellow men, even children," Rodger wrote. "How ironic is it that my father, one of those men who could easily find a girlfriend, has a son who would struggle all his life to find a girlfriend."

But the overarching theme of the manifesto focuses on his frustrations with women.

"My orchestration of the Day of Retribution is my attempt to do everything, in my power, to destroy everything I cannot have," Rodger wrote.

"All of those beautiful girls I've desired so much in my life, but can never have because they despise and loathe me, I will destroy. All of those popular people who live hedonistic lives of pleasure, I will destroy, because they never accepted me as one of them. I will kill them all and make them suffer, just as they have made me suffer. It is only fair."