MINNEAPOLIS — Answering an online ad for a nanny job — which she had done at least twice before without trouble — cost Katherine Ann Olson her life, authorities said.

Olson, a 24-year-old St. Olaf College graduate, was found dead in the trunk of her car Friday night. She was last seen by friends on Thursday morning, when she went to meet someone in Savage, Minn., about the job, which authorities said she had found on Craigslist.

A 19-year-old Savage man who police think placed the ad is being held pending charges. Authorities did not release his name.

Olson had taken nanny jobs at least twice before, including a job in Turkey, after answering online ads.

Olson's family gathered in front of their Cottage Grove home Saturday afternoon to share stories of a vivacious young woman "who was a joy, who trusted people."

Her family said they'd had misgivings about Katherine Olson finding jobs online. But she never seemed to worry.

"She always assumed the best in other people," said her father. "She assumed the best of this appointment Thursday morning. And, if it didn't work out, she assumed she could turn around and go home."

Craigslist.org, an online bulletin board, has fallen under the watch of law enforcement agencies in recent years because of prostitution ads and its use to set up robberies, but an Internet search revealed no other homicides connected to the site.

Savage Police Capt. David Muelken gave this account of Olson's death:

A resident told a Savage Public Works employee about a purse found in a garbage can at Pacer Park. That employee notified police, and an officer got the purse, which contained things belonging to Olson.

At first it appeared to be a theft. Police called Olson's home and left a message telling her they had her purse.

About 5 p.m. Friday, Olson's roommate returned the call and told police Olson hadn't been seen since 8 a.m. Thursday.

Police went back to Pacer Park and found a garbage bag in the container. Inside the bag was a "significantly bloody towel."

As the search proceeded Friday night, other investigators began to focus on the 19-year-old man from Savage.

"We're confident we have the suspect in custody," Muelken said. He said he believed there is no public threat.

Nancy Olson, the victim's mother, said, "We grieve even more because of what the world has lost. Not just for us, but for all these other people she would have touched."

"Parents get to raise a child and then release them to the world. And now she's gone to the next world," Nancy Olson said. "We've had her for the time we had her. And now we've given her away."