A plot to "shoot up" a western North Carolina high school was derailed by tip from a teen who chatted with the suspect online, authorities said Thursday.

Investigators took a 15-year-old boy into custody Friday and found at his home a computer and DVD with plans for an attack on Brevard High School, Transylvania County Sheriff's spokesman Lt. Brian Kreigsman said. Kreigsman said the plans were not elaborate, and would not say whether weapons were found.

Kreigsman said the teen told a 16-year-old girl from New York earlier that day that he planned to "shoot up a school" on Monday. The two were chatting on the MySpace social networking Web site.

"The potential was here for this to be a major threat," Kreigsman said.

The girl pulled the boy into a private chatroom to get more information, Kreigsman said, and he referred to a shooting in Greensboro in 1979 in which white supremacists killed five people and wounded 10 others.

The girl told authorities that the boy, who also referred to himself as the "Grand Dragon," then abruptly ended the conversation.

After the online chat, the girl notified local authorities, which contacted North Carolina law enforcement.

Kreigsman declined to identify the teen, who's undergoing a mental-health evaluation. No charges had been filed Thursday afternoon.

Brevard County Schools spokeswoman Dian Brewton said the suspect, who isn't currently a student at the 750-student high school, had been in a mental health facility. He was home waiting to be transferred to another one when he was taken into custody, she said.

Security at the high school hasn't been changed because of the plot, she said.