Together, they envisioned a bloody assault on students and staffers at a Long Island high school, chillingly planning it for the ninth anniversary of the deadly Columbine High School rampage, Suffolk County police said.

"I will start a chain of terrorism in the world," the 15-year-old wrote in one of several alarming journal entries, according to police. "This will go down in history. Take out everyone there. Perfecto."

The two students were arrested Friday in the alleged plot at Connetquot High School in Bohemia, about 50 miles east of New York City. Both were charged with misdemeanor conspiracy, punishable by up to a year in jail.

Local students and parents shuddered at the description of the plot, which police said was fleshed out in a videotape that identified several potential victims by name.

"They're not really afraid to do anything," said Joseph Welischar, a Connetquot student who said he knew the suspects. "So, yeah, it's kind of scary."

It was more than scary to Dawn Wiegard, a mother of two Connetquot students.

"It's devastating," she said.

The 15-year-old, a Connetquot student whom authorities identified as the driving force behind the plan, did not enter a plea when he appeared in juvenile court Friday. A judge ordered two weeks of medical evaluation at the Sagamore Children's Hospital, according to Newsday. The teen's mother and stepfather were in the courtroom but would not comment.

A former friend who said she believed she was one of the 15-year-old's targets told Newsday the suspect was an emotionally troubled boy riveted by violence, and particularly by the 1999 Columbine High School massacre in Colorado, in which two gunmen killed 12 fellow students, a teacher and themselves.

"I do remember him being fascinated about blowing up things," said Briana Valentino, 15, who said she and the suspect had been close friends before he suddenly became hostile to her a month ago. "I remember him showing me videos of crazy shootings online."

The other suspect, 17-year-old Michael McDonough, pleaded not guilty at his arraignment Friday. His Legal Aid Society lawyer, Robert Flick, said his client was "barely" culpable, according to news reports.

McDonough's father told the court that his son, who attended Sachem North High School, was receiving mental health counseling.