Cops: Calif. school plotters sought "horrific tragedy"

South Pasadena High School in South Pasadena, Calif.

CBS Los Angeles

SOUTH PASADENA, Calif. - Police said they prevented a "horrific tragedy" by arresting two teenage boys who plotted to kill three high school staffers then gun down as many students as possible in the quaint Los Angeles suburb of South Pasadena.

The boys, ages 16 and 17, had been under constant surveillance since the school district informed police of their plans last Thursday, South Pasadena police Chief Art Miller said Tuesday. Miller said the district was notified of the plot by a community member.

After being notified of the threat, authorities conducted Internet surveillance and determined that the boys "were making a huge plan of a school massacre," Miller said, adding that the boys identified three staff members at the school by name and planned to kill as many students as possible.

The teens were arrested Monday after authorities executed search warrants and retained computers as evidence. Miller said that the case would be presented to the district attorney for filing consideration later Tuesday.

Miller said there didn't appear to be a target date for the attack, but noted that the teens had a "very, very specific plan of how they were going to carry out their sick mission."

He said the boys researched weaponry, how to make explosives, how to disarm people and they also reached tactical elements - like "how to go in and be the aggressor with firearms."

Authorities have not named a motive in the case, citing an ongoing investigation.

The boys were both about to begin their senior year at South Pasadena High School, a well-regarded school. The leafy San Gabriel Valley suburb of about 25,000 people 6 miles from downtown Los Angeles is known for its high-quality schools, which drive up the price of homes. Small two-bedroom bungalows can easily top $700,000.

The parents of both boys have been cooperating, Miller said. He also indicated that the teens had spoken "very cold-heartedly" of the plot with investigators.

The arrests came the day after another Los Angeles County boy was arrested on suspicion of posting online threats to shoot students at local schools, though sheriff's officials acknowledged that those threats were intended as pranks.

The South Pasadena district is scheduled to begin classes on Thursday. Miller said that off-duty officers will be present to ensure students feel safe.