A Montgomery County Court 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, 14, and his mother, Michele Cossey, 46, "the most unhealthy I've seen in a long time."

Tressler said that in two-thirds of juvenile delinquency cases, the parents were at fault. "You're one of those," he said in comments directed to the teenager.

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

Cossey was arrested in October for plotting an attack on Plymouth Whitemarsh High School.

The judge said the parents' lack of discipline and the mother's obsession with her son - culminating in her decision to buy him guns - led to his emotional problems.

Police found an arsenal of weapons in his bedroom on the day of his arrest. The cache included a 9mm assault rifle purchased by his mother.

Michele Cossey encouraged her son to have a "her and I against the world" mentality that desocialized the teenager, the judge said.

He ordered Cossey to be sent to 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 Michele Cossey and her husband, Frank, during the next 45 days.

The judge said the parents could have no contact with their son for three months. After that, visits can occur only if the teen and his parents both change their behavior with each other.

"You will never do this to my community again," said Tressler, referring to the terror that Cossey's plans and his arsenal generated.

Cossey had no ammunition for the weapons, and some officials have said no attack was imminent. Tressler appeared to address that issue in his remarks to the son.

"You say, 'Well, gee, Judge, I wouldn't have done it,' but how are they supposed to know that?" Tressler asked.

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

Cossey's mother, who sobbed intermittently during the judge's remarks, had no comment as she left the courtroom. She is awaiting trial on charges that she illegally bought her son three guns.

Frank Cossey stopped to thank the prosecutor, District Attorney Bruce L. Castor Jr., for his "intervention." Later, he told reporters that he and his wife "probably deserved" the judge's harsh words.

Castor also called the judge's rebuke "warranted."

Dillon Cossey's attorney, J. David Farrell, said he preferred to focus on "outstanding" reports on his client's behavior and schoolwork at the youth center where he has been living since his arrest.

In two months, the teen has realized that he was fixated on a "poisoned environment" on violent Web sites, Farrell said. "Like an addict in detox," he said.

As for the teen's treatment program, Farrell said: "I think he's going to excel."

The judge also had harsh words about the Columbine shooters, Dylan Klebold and Eric Harris, whom Dillon Cossey idolized, even naming one of his guns for Harris. Tressler said the two have come to be 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."

Contact staff writer Kathleen Brady Shea at 610-702-7625 or kbrady@phillynews.com.