A 15-year-old freshman at San Rafael High School was raped on campus after walking to school Monday morning, and a 26-year-old suspect was arrested a short time later when he was seen dragging the girl by her neck, police said.

Jorge Alberto Ek-Luna, a San Rafael resident, was booked into Marin County Jail on suspicion of rape, assault, kidnapping, lewd and lascivious conduct with a 14- or 15-year-old child, damaging a wireless communications device and providing false identification to police.

Bail was set at $750,000, and Ek-Luna was expected to appear in court this afternoon.

The incident began around 8 a.m., when the girl, a freshman from the Canal Area, was walking to school alone on Third Street. The girl told police she remembered passing Ek-Luna at Third and Union streets on the way to school.

As the girl turned on to campus, the suspect approached her from behind in the parking lot, held a broken bottle to her throat and took away her cell phone. Then he forced her into some bushes next to a school building and raped her, police spokeswoman Margo Rohrbacher said.

After the assault, he used the jagged bottle to force the girl off campus, saying he wanted to take her to a motel, Rohrbacher said. But a passing motorist, seeing the attacker dragging the girl by the neck on Francisco Boulevard East, called 911 at 8:43 a.m.

Police arrived and found the pair on Francisco Boulevard East near Hoag Avenue. Ek-Luna was arrested and the girl was taken to Marin General Hospital, where she was treated and reunited with her family, Rohrbacher said.

The case is still under investigation, but police said the incident appears to be a random attack and that the victim does not know Ek-Luna.

"It doesn't look like he was stalking her," said San Rafael police Detective Harry Barbier. "It looks like a crime of opportunity."

Although the girl was accosted on Third Street - in view of the parking lot, athletic fields and passing traffic - no one reported seeing the girl being forced into the bushes, Barbier said.

Many students were still unaware of the incident by late Monday afternoon, but school principal Judith Colton advised parents in a letter posted on the school Web site and sent out on an email list. The letter will be distributed to students this morning, school district spokeswoman Leah Reich said.

Laura Alvarenga, the San Rafael City Schools superintendent, said she did not know whether new security precautions would be implemented, but she said counselors will be available for students who need them.

"We believe that this is a very sad incident and most unfortunate, and it was perpetrated by an outsider," Alvarenga said. "We will certainly make available a support system for the students."

Anyone with information about the incident is asked to call San Rafael police at 485-3000.

Police were still investigating Ek-Luna's background Monday and it was not clear how long he has been in San Rafael or whether he has a criminal record. Police said he is unemployed.