SANTA BARBARA, Calif. (KABC) -- The Isla Vista killer had researched Nazis and ways to kill silently before a murderous rampage last May, the Santa Barbara County Sheriff's Office revealed in a new report.



The 64-page report, which details how the killer carried out the rampage on May 23, completes the investigation of the events that left six UC Santa Barbara students dead and concludes that he acted alone.



Elliot Rodger, 22, fatally stabbed three men in his apartment. He then went on a drive-by shooting spree, killing three more people, and deliberately hitting people in the street with his car. Fourteen others were injured.



Rodger was involved in two gun battles with sheriff's deputies and was wounded before killing himself.



Investigators say Rodger trained and prepared methodically a year in advance. The report reveals that Rodger spent more than $2,000 buying weapons, guns and ammunition.



The three stabbing victims were killed separately as they entered the apartment at different times. Each was stabbed multiple times by a large hunting knife, and all were likely ambushed.



A search of Rodger's browsing history on his laptop showed he searched for the phrase "quiet silent kill with a knife," and he was "very interested in the practices and techniques of the Third Reich."



Stab and slash marks on a fitted sheet and several pillows suggest Rodger rehearsed his actions.



The report goes on to say Rodger posted the now-infamous confessional on YouTube a few minutes before he drove to a sorority house, where he opened fire on three students standing outside. Two of them died, and a third survived. He continued on to a nearby convenience store, shooting and killing another student.



As investigators looked at what can be done to prevent a similar crime in the future, they stated, "there is no single or simple solution to the complex problems that lie beneath that question."



The report states "In California, we have some of the strongest gun control laws in the nation, yet in this case the suspect was still able to legally purchase and possess three handguns and hundreds of rounds of ammunition."



The suspect was receiving treatment for mental illness and had been since childhood, the report noted.



"What is unusual in this case is the extent of the written and video-taped record of thoughts, feelings and intentions left by a suspect, who in retrospect, clearly suffered from significant mental illness that ultimately resulted in homicidal and suicidal rage," the report stated.



In a final handwritten journal entry dated that day, he wrote: "This is it. In one hour I will have my revenge on this cruel world. I HATE YOU ALLLL! DIE."



Rodger's father, Peter, says he hasn't read the entire report, but he has "nothing but respect" for how investigators did their job and treated his family. He said he also hopes the new findings help sheriff's officials avoid future tragedies.



The Associated Press contributed to this report.



