A bizarre and cruel Internet hoax that ended with the suicide of a 13-year-old girl has bitterly divided a western St. Louis suburb, provoked a firestorm in the blogosphere and raised troubling questions about how to police traffic on popular social networking sites such as MySpace.com.

The death of Megan Meier in Dardenne Prairie, Mo., went beyond the growing phenomenon of cyber-bullying because the alleged instigators of the hoax were not only adults, but parents of a classmate of Megan's, who lived just down the street from her.

"People are just totally shocked. ... They can't believe that an adult would have done this," said Pam Fogarty, mayor of the town of 7,000 people.

"The scary part is that when you look at the blogs and listen to the phone calls we're getting, it's very quickly becoming a mob mentality," said Fogarty, who has arranged for additional police patrols in the neighborhood.