An 18-year-old Gunn High School student, Weston Healy, was arrested Thursday afternoon for possession of a weapon on a school campus, following a dramatic police lockdown of the south Palo Alto facility.

Healy was taken into custody shortly before 3 p.m., about an hour after a city worker called police to report that two men had driven onto campus. One appeared to be armed with an assault weapon, which later was found to be an Airsoft rifle, according to police.

Airsoft rifles shoot BB-sized plastic pellets.

Also located in the vehicle were two face masks, one spade shovel with a 4" pick, a hatchet with a removable saw, and a military style knife with a 7" blade, according to a police press release.

It is a felony to possess a knife, gun or other weapon on campus, Police Lt. Sandra Brown said Thursday. Campus includes not just the academic buildings but also the parking lot and athletic fields, she added.

Police officers, including a SWAT team, immediately responded to the 911 call, locating the unoccupied vehicle in the school parking lot. Police called for a "Code Red," initiating the school's lockdown, officials said.

School administrators and police located the two suspects inside a classroom, both of whom were Gunn students and who admitted to possessing the rifle.

Other Gunn students were ordered to stay in the classrooms and other buildings during the incident. Several reported not knowing why the school was in lockdown and feeling afraid.

Students were released from the school shortly before 3 p.m.

Gunn issued an e-mail statement to families at 3:56 p.m.

"This afternoon as students were leaving class, Gunn experienced a Code Red as a safety precaution.

"At no time were students or staff in danger," the Gunn statement said. "Students and staff did an excellent job of following the Code Red procedure and the Palo Alto Police Department's response was immediate and extremely effective."

During the incident, police received a separate report of possible gunshots in the area of Los Robles Avenue, near Gunn, and a report of a Gunn student being held hostage by a gunman. The gunshots were unsubstantiated, and the hostage claim turned out to be a misunderstanding between a student and parent, the police stated.

Parents arriving to pick their children up were diverted to Alta Mesa Cemetery across Arastradero Road from Gunn while police and school officials concentrated on room V9 in the portables section of the school.

Other parents waited in cars along Miranda Avenue and on Arastradero until cones barricading the campus entrance were removed. Many were on cell phones attempting to reach their children inside the school.

One student reported that desks has been pushed up against the inside of the door of the classroom.

As students poured out of Gunn following the lockdown, the campus still swarmed with police.

One student said she had been confined in the school's main office with staff, while other students said they had been held in classrooms or the school's library. They were unsure of the cause of the disturbance or whether those detained were Gunn students or outsiders.

Gunn officials stated Friday morning that disciplinary procedures will follow for Healy and the second student involved, who has not been named. In addition, a third student was detained during the incident but was found not to have been involved and was immediately released.