FRESNO  (AP) — Police are trying to identify the man who attacked and robbed a Central Valley elementary school teacher working on campus over the weekend.

Fresno police Lt. Joe Gomez says the teacher was coming out of a bathroom at Teague Elementary School on Saturday evening when the attacker pushed her back inside and knocked her down.

Gomez tells KFSN-TV the man, who covered his face with a shirt, tied the teacher up and punched her in the face several times; he stole her ring and cellphone and threatened to hurt her even more.

School officials believe it was an isolated incident, but they have increased police patrols on campus as a precaution.

Police are reviewing surveillance video to try to identify the attacker.