Armed with a knife, David Velasquez of Redwood City confronted a 29-year-old San Francisco woman in the garage at 890 Broadway around 6 p.m. that day, Redwood City police said.
He grabbed the woman and was forcing her toward her vehicle, police said. The woman struggled and was forced to the ground. A witness entered the garage, saw what was happening and yelled at the attacker, who ran off, police said.
The victim, who is an employee at Summit Prep, suffered minor injuries in the scuffle.
An investigation led police to Mr. Velasquez, who is being held in San Mateo County jail on suspicion of kidnapping, assault with intent to rape, false imprisonment, and making terrorist threats.
The motive appears to have been sexual assault, police said.
Police ask that anyone with information about this incident call police at 780-7100, or the anonymous tip line at 780-7110.
Todd Dickson, executive director of Summit Prep, said the incident is unprecedented for the school.
He said Jan. 24 he has been working, in consultation with the faculty, most of the day preparing a statement for parents and students. His plan, he said, is to address what happened, point out how Summit is a safe school, and explain what might be done to make the school even safer.
"It's a scary event (and) an opportunity to improve the safety of the family-like culture of this school even more," he said.