(CNN) -- Police in San Mateo, California, said Monday that "a potentially very drastic event" at a high school was averted when school personnel subdued a former student who walked into the school armed with pipe bombs, a chainsaw and a 2-foot-long sword.
At least 1,200 students and faculty were evacuated from the northern California school.
"It had the potential to be a catastrophic incident," said police Lt. Mike Brunicardi, describing the incident in which two pipe bombs exploded and at least 1,200 students and faculty were evacuated from the Northern California school.
No one was injured in the incident, police said.
Brunicardi said a 17-year-old former student wearing a nylon vest packed with 10 homemade pipe bombs entered Hillsdale High School in San Mateo about 8 a.m. Monday. He detonated two devices, with smoke setting off the school's fire-alarm system, before two teachers confronted him.
"The suspect was quickly wrestled down by a teacher who, with the help of the principal and another teacher, were able to hold him down until police arrived minutes later," Brunicardi said.
The suspect's intentions were not clear, police said.
"He's being interviewed right now, but we don't have his specific motives at this time," Brunicardi said, adding that while the explosive power of the pipe bombs was not immediately known, the teachers who subdued the suspect put themselves in jeopardy.
"We are relieved that no one was injured and it's fortunate that we were able to apprehend the student before he hurt himself or anyone else," said San Mateo School District Associate Superintendent Kirk Black said.
Authorities said the suspect, whose name was not immediately released, had been a student at the school in 2008.
CNN's Nick Valencia contributed to this report.
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