Police converged on Hillsdale high in San Mateo after a former student came back to campus carrying pipe bombs.
Hillsdale High School in San Mateo will be closed again Tuesday after a near-disaster was averted Monday morning.
Police say a former student walked into the school just after classes began Monday carrying a cache of weapons.
The 17-year-old set off two pipe bombs before being tackled in a hallway by three teachers.
The suspect was found carrying eight more pipebombs in his vest. He also had a chainsaw and a sword with him, according to police.
Police flooded the campus of Hillsdale High School in San Mateo Monday morning. Students were seen leaving the area by the hundreds after authorities canceled classes for the day following the explosions.
The students gathered at a large black top area behind Abbott Middle School about a block away from the school. That is where the school told parents to pick their children up from school.
Police were called to the school at 8:07 a.m. after reports that someone brought a gun on campus. While police were on their way, they heard reports of an explosion.
Kaela Murphy said is was really scary because she knew the suspect was right outside her classroom door. "He could have killed our whole class," Murphy said.
Parent Lisa Souther said when she got the news she immediately thought of Columbine. "That's exactly where my brain went. So it was scary, very scary," Souther said.
An assistant superintendent for the district Kurt Black said the explosions did not do any damage and nobody was hurt. Black said the teachers knew the student and somehow were able to take hold of him until police arrived. The unidentified student is now in police custody.
One student who was on campus described the sound of one of the explosions as "a thousand M-80s going off."
Another student said her teacher ordered everyone to get under their desks after he noticed smoke in the hall. That girl said she saw a guitar case, a chainsaw, a pipe and some brown liquid in the hallway as she ran out of the school.
Someone else said he saw a kid running down the hall carrying pipe bombs in his arms with a counselor running after him after he heard what he described as an explosion.
A bomb-detecting robot arrived at the scene just after 9 a.m.
Hillsdale High School is one of the biggest high schools in San Mateo with 1,200 students. Classes started last week.
Police from several area cities were called in to help block off the scene.
Police closed several blocks around the school including 36th Street and Alameda. Bomb squads along with the robot went through the high school room by room to make sure there were no other devices inside the school.
The line of parents waiting to pick up their children was two city blocks long at one point as officials checked identification of each person before releasing a student to an adult.