SOUTH PASADENA, Calif. -- Investigators acting on a tip unraveled a plot to carry out a mass shooting at a suburban Los Angeles high school, arresting a pair of students who planned to target three school staff members and kill as many people as possible, police said Tuesday.
School officials learned of the plot last Thursday and notified detectives, who began watching the 16- and 17-year-old boys and monitoring their online activity, South Pasadena Police Chief Arthur Miller said.
The pair didn't have a date for an attack or weapons, but their online messaging included the names of three staff members to target and threats to randomly kill students, Miller said.
They were also researching automatic firearms, handguns, knives, explosives and tactical techniques, he said.
"Three or four days' worth of surveillance on the Internet indicated that they had a very real threat," he said. "They had a plan in mind that they were going to execute."
The names of the teens have not been released because of their ages. Police expected to present their case to the district attorney later in the day.
Miller said police interviewed the teens and realized how cold-hearted the plot was. He provided no specifics, and officials at South Pasadena High School did not disclose details of the initial tip.
Classes start again Thursday in the San Gabriel Valley suburb known for its quality schools and community involvement in education. Police plan to have a larger presence than usual on campus for the first day of school.
School cheerleaders Zoe Bullard and Leah Schexnayder, both 16, said they were frightened by news of the arrests.
"I don't even want to go to school Thursday, because what if something happens?" Schexnayder said.
"What if they missed a person?" Bullard asked about the police investigation.
Miller said his officers saved lives by thwarting the attack in the town of about 25,000 people about 6 miles from downtown Los Angeles.
"They were making a huge, a huge plan of a school massacre," Miller said. "They just wanted to kill as many people as possible."
Enough evidence was gathered to serve warrants at the teens' homes Monday.
Police had to break into one teen's house as he resisted arrest, and they took him into custody as he tried to run, officials said.
One of the teens purportedly said he had a relative with a gun that he might be able to get. Police contacted that relative, who said the weapon was secured.
The two teenagers, who were about to become seniors, were arrested on charges of conspiracy and making threats. They were being held at a facility for youthful offenders.
Miller didn't provide information about the dynamic of the suspects' relationship. He said their parents were cooperating with investigators.
The FBI joined the investigation to help search for evidence on the computers seized from the teens' homes.
Officials must investigate all threats and decide how to deal with students who make them, said Ken Trump, president of the National School Safety and Security Services, a consulting firm.
"They're better off to find dozens of threats that are not credible than to have one case that's missed," he said.
Trump said the South Pasadena threat was reasonably well-developed based on information police have released.
Information for this article was contributed by Justin Pritchard and Raquel Maria Dillon of The Associated Press.
A Section on 08/20/2014