Last month, Youens, armed with a gun and the location of the dentist's office where Boyer worked, shot her to death, then killed himself.
The shootings took place Oct. 15 in Nashua, N.H., where Youens, 21, and Boyer, 20, had gone to school.
Youens' thoughts and plans are detailed in a police report drawn partly from the Web sites where he debated with himself whether to kill Boyer, kill another former classmate, or storm into Nashua High School and kill as many people as he could, the Boston Globe reported yesterday.
Youens paid hundreds of dollars to online research services to determine Boyer's birth date, Social Security number, home address, and workplace address.
"It's actually obsene [sic] what you can find out about people on the Internet," he wrote.
Boyer's stepfather, Tim Remsburg, said he was considering suing Geocities and Tripod, the two online companies where Youens maintained his Web sites.
Although both Youens and Boyer graduated from Nashua High in 1997, friends and family say the woman was not aware of Youens or his obsession with her.
Youens' online journal chronicles the one-way relationship, recounting a humiliating day when Boyer brushed past him in the school lunchroom, and a Valentine's Day when he realized she had received a rose from a boyfriend.
He also recalled realizing in the 10th grade that he was in love with her, and deciding shortly thereafter to kill her and himself, the Globe said.
"That was the basic plan for the next half decade," he wrote.
But Youens, who dropped out of college after a year and was living with his parents, found it difficult to stalk Boyer, in part because she often was surrounded by family. So he turned to online research services to track her.
Remsburg said he was angry that Geocities and Tripod did not monitor their content and that Youens was able to use Internet companies, including Docusearch and Infoseekers, to hunt down personal information.
Internet companies say that monitoring content is not technologically feasible. Federal law protects Internet service providers from liability for material posted on Web sites.
A Tripod official said that almost no one visited Youens' site and that they would have told police about it had they seen it. Tripod officials said they eliminated Youens' site as soon as police notified them about it.
A Geocities spokesman declined to comment on Youens' site.A spokeswoman for one research agency told the Globe that the information it sells is gathered from public sources such as court or motor vehicle records.
© 2000 Philadelphia Newspapers Inc.