PALO ALTO, Calif. — Grim news hit this university town in late October just two days before a PTA forum on teenage stress: A fourth Palo Alto teen had died after stepping in front of a commuter train in less than six months.

With hundreds of parents crowding the forum, school Superintendent Kevin Skelly told the anxious gathering that the latest death was "a cruel irony" because city officials were working to prevent another tragedy.

Experts have struggled to understand what generates clusters of teen suicides, a phenomenon that breaks into a community's awareness when they occur in a public place, as they did in Palo Alto. But officials in this San Francisco peninsula city of about 59,000 say they're deploying a wide array of approaches to stop it from growing.

Those efforts are moving with greater urgency since the most recent suicide on Oct. 19 that involved a 16-year-old male student at Henry M. Gunn High School. Two other Gunn students, a 17-year-old boy in May and a 17-year-old girl a month later, also took their own lives on the train tracks. A 13-year-old girl died the same way in August, days before she was to become a Gunn freshman. At least one Gunn student, another 17-year-old boy, was prevented from killing himself in June after his mother followed him to the tracks.

"There is no single answer. There is not necessarily a cumulative set of answers either," said Greg Hermann, a spokesman for Palo Alto, which convened a task force of psychologists, clergy and others to prepare a response plan. "There are intelligent steps we can be taking."

Police patrol the tracks while city officials negotiate with the railroad on a design to make them less accessible. Students are discouraged from erecting shrines at the sites, which might romanticize the deaths, and the media has been asked not to make public those locations.

Some of the high school's 1,900 students also have created T-shirts with the message "Talk to Me" and formed pacts not to harm themselves. One student left bracelets made of heart-shaped walnut shells for others in need of cheering up to find. A group posts optimistic notes around campus.

Joyce Liu, a 17-year-old senior, created a peer-run support group that staffs a table during free periods and hosts a social networking site where classmates can find someone to listen. She also created a Web site called "Henry M. Gunn Gives Me Hope," where teachers and students share random acts of kindness and beauty that have come their way.