Police in Minnesota said an online ad may have cost a young woman her life.

Katherine Olson was found dead in the trunk of her car at 10 p.m. Friday at the Kraemer Nature Preserve in Burnsville, a south suburb of Minneapolis.

Police said Olson was last seen by friends when she went to meet someone about a nanny job posted on Craigslist.org, an Internet bulletin board.

Savage police aren't naming the suspect until he is charged, which could happen Monday or Tuesday. The Minneapolis Star Tribune reported Monday that a friend of the 19-year-old man in custody was shocked.

"I couldn't see him doing something like this," Steve McCutchan told the Star Tribune. McCutchan reportedly was questioned about the suspect Saturday.

McCutchan told the newspaper that the suspect had used Craigslist.org to find parts to fix his go-kart and sport utility vehicle, which were hobbies of his.

"He's a pretty good guy," McCutchan said, adding that nothing seemed unusual about the suspect's behavior the last time they spoke, about a week ago. "He was happy, smiling, laughing. I don't believe it was him."

Police declined to say how the 24-year-old Olson was killed.

Olson graduated from St. Olaf College last year. Her family said she had taken nanny jobs at least twice before after answering online ads.