A Pennsylvania teenager who confessed to planning a school attack chatted online about the Columbine disaster with a Finnish teenager who recently shot dead eight classmates.

Dillon Cossey, 14, was arrested in October for allegedly plotting a shooting spree at Plymouth Whitemarsh High School near Philadelphia. Cossey's attorney, J. David Farrell, said his client communicated with Pekka-Eric Auvinen, the Finnish teenager.

"They had discussed certain video games and shared videos with each other," Farrell said. "Obviously, Columbine was a shared topic of interest."

The teen was "horrified" when he heard about the Finnish attack, Farrell said.

Finnish police searched Auvinen's computer, finding evidence that Cossey communicated with the 18-year-old shooter. Auvinen killed six students, a nurse and the principal in Tuusula, about 30 miles north of the Finnish capital of Helsinki. He then shot himself in the head, and died hours later at a hospital.

Until now, teenager killers were depicted as loners but Cossey and Auvinen's communication shows that potential killers may be sharing information over the Internet, according to a report.

Click here to read Times of London article on shared massacre plots.

The two teenagers likely communicated over two MySpace Groups, "RIP Eric and Dylan" — in reference to Eric Harris and Dylan Klebold, who killed 12 classmates at Columbine.

In Pennsylvania, detectives were running the name of the Finnish shooter through the computer seized from Cossey, who admitted in juvenile court to planning an attack.

"We had heard when we first got this guy that he had contacted other people through Web sites," Plymouth Township Deputy Chief Joe Lawrence said. "We wouldn't be shocked by it."

Tipped off by a boy Cossey tried to recruit, Pennsylvania authorities searched his home last month. They found a rifle, about 30 air-powered guns modeled to look like higher-powered weapons, swords, knives, a bomb-making book, videos of the 1999 Columbine attack and violence-filled notebooks.

Cossey told a friend that he wanted to pull off an attack similar to Columbine. Prosecutors and Farrell have said he felt bullied.

Two weeks after his arrest, Cossey admitted to three felonies — criminal solicitation, risking a catastrophe and possession of an instrument of crime — in Montgomery County juvenile court. He is now in juvenile custody, where he could remain for up to six-and-a-half years.

Authorities have accused Cossey's mother, Michele, of helping him build his weapons stash. She is charged with illegally buying her son a .22-caliber handgun, a .22-caliber rifle and the 9 mm semiautomatic rifle, which had a laser scope. Her preliminary hearing is scheduled for Dec. 13.

Farrell said he doesn't know whether Dillon Cossey had contact with other people who could pose similar threats, but planned to explore that possibility with investigators and his client.

The Associated Press contributed to this report.