A Montgomery County judge sharply criticized the mother of a teenager charged with plotting a Columbine-style attack and then ordered her son to enter a juvenile treatment program near Pittsburgh.

Judge Paul Tressler called the relationship between Dillon Cossey. 46, and his mother, Michele Cossey, "the most unhealthy I've seen in a long time."

Tressler said in two-thirds of juvenile delinquency cases, the parents are at fault. "You're one of those," he told Cossey.

Cossey was arrested in October for plotting an attack on Plymouth Whitemarsh High School.The judge said the mother's lack of discipline and obsession with her son, culminating in her irresponsible decision to buy him guns, led to his emotional problems. Those difficulties surfaced when police found an arsenal of weapons in his bedroom on the day of his arrest. The collection of weapons included a 9mm assault rifle purchased by his mother.

"Your mother loves you, but she's not very good at being a mother," said Tressler. "It's as simple as that."

The judge ordered that Cossey be sent to the George Junior Republic, a residential treatment program in Western Pennsylvania. His time there will be dictated by the progress of his recovery.

The judge also ordered psychiatric and psychological evaluations for both Michelle Cossey and her husband, Frank, during the next 45 days. The judge also said the parents could have no contact with their son for at least three months. After that, visits can occur only if the teen and his parents both earn them.

"You will never do this to my community again," said Tressler, referring to the fear that Cossey's plans and his arsenal generated. "I will never release you until you're ready."

In the juvenile system, Dillon Cossey could remain in custody until he turns 21.

The judge also had harsh words for Dylan Klebold and Eric Harris, whom Dillon Cossey idolized as the Columbine shooters. He said the pair are inaccurately viewed as heroes by young people who have been bullied.

"They weren't responding to bullies," the judge said, pointing out that both had a criminal history. "They were arrogant and they weren't going to follow the law."

Cossey's mother, who sobbed intermittently during the judge's remarks, had no comment as she left the courtroom.

Her husband stopped to thank the prosecutor, District Attorney Bruce Castor, for his "intervention."

Contact Kathy Brady Shea at 610-702-7625 or kbrady@phillynews.com.