Updated

The father of a teen accused of plotting a Columbine-style massacre at Marshfield High School (search) said his son was framed by a former friend following a dispute over a girl.

Sixteen-year-old Tobin Kerns was arrested Sept. 17 after police turned up evidence of his alleged plan to carry out an attack that would coincide with the sixth anniversary of the Columbine (search) shootings on April 20, 2005.

"There were specifically identified teachers, there were specifically identified students who were going to be murdered," Marshfield Police Chief William Sullivan said at a news conference Wednesday.

Ben Kerns told reporters that his son was innocent. He said his son hung out with three friends from school, who called themselves NBK, for "Natural Born Killers," a movie about a couple who go on a killing spree. He said his son may have discussed plans for violence, but he didn't think they would have carried out the plan.

He said one of the other teens was the ringleader, not his son.

"I think it was a bunch of hot air," he said. "There was no real threat. Nobody had guns. Nobody had access to guns."

Police said a search of the woods near Kerns' home found evidence that an explosive had been detonated as a test. A Sept. 17 search of his home allegedly turned up diagrams of the school, including plans for which exits should be padlocked to prevent escape. Police also found information downloaded from Web sites about weapons dealers and bombs.

Ben Kerns said his son was treated for post-traumatic stress syndrome (search) this summer after considering suicide. He said he hasn't associated with the three other boys since he was discharged from the program in July.

Kerns said his son recently had a falling out with one of the three teens, who spread a rumor that he'd slept with Tobin's girlfriend. He speculated that the dispute may have prompted the teen to tell police about the alleged plot and say his son was the ringleader.

Tobin Kerns was arraigned in juvenile court Sept. 20 on eight charges of threats to commit a crime. He was arraigned the next day on additional charges of promotion of anarchy and attempted murder.

He was ordered held without bail. At dangerousness hearing last Thursday in Plymouth, he was found to be a danger to the community and was ordered held without bail for 90 days.

Toby Kerns, as he's known, had several past run-ins with police, his father said, including a break-in at a summer house in Marshfield, vandalism at an elementary school in town and a break-in at a liquor store. But Ben Kerns said his son has had no problems for the past two years.

"This kid is really trying to turn his life around," he said.

Some Marshfield parents and students were angry that authorities waited until Wednesday's news conference, three weeks after Kerns was arrested, to describe the plot.

"As a parent of a child at the high school, I'm furious," said Jim Hoey of Marshfield. "We have a right to know right away and to discuss these things with our children."

School Superintendent Thomas Kelley said school officials did not want to jeopardize the ongoing police investigation.

"Had we thought there was a safety issue at this school, we would have taken action," he said. "It was really a police matter, and it was clear to us that a threat was eliminated by the arrest within a short window of time."