FBI agent Mark Holstlaw says Michael Ian Campbell of Cape Coral, Fla., confessed to agents Wednesday that he used the screen name "Soup 81" to send the threat over AOL's instant message system to Columbine student Erin J. Walton.
Authorities in Florida had executed a search warrant and seized computer equipment from Campbell's Cape Coral home. He was charged with transmitting a communication containing a threat in interstate commerce, according to a complaint and an affidavit by Holstlaw, both released by the Justice Department here.
The threat was sent to a 16-year-old Columbine student from a user with the computer alias Soup 81. The message warned her not to go to school Thursday, said Jefferson County sheriff's spokesman Steve Davis said.
"I need to finish what begun (sic) and if you do I don't want your blood on my hands," it read in part, Davis said. Agents were trying to find the sender.
Students of Columbine High School started their Christmas break two days early after the threat forced officials to cancel classes Thursday and Friday, reports CBS National Correspondent Hattie Kauffman.
Critics of Jefferson County authorities have said they ignored threats Eric Harris and Dylan Klebold posted on the Internet before their April 20 attack on the school. They killed 12 students and a teacher before committing suicide.
Officials took no chances this time, deciding to begin the winter holiday break two days early for the school's 1,980 students and its faculty and staff.
Authorities searched the building and found nothing, officials said. But "in the interest of the safety and emotional well-being of our community, we canceled classes," said school district spokesman Rick Kaufman.
Sheriff's Division Chief John Kiekbusch said it is possible the writer knew the girl was a Columbine student through her AOL user profile.
Thursday would have been the last day of classes for most students, with many scheduled to take final exams. Friday was to have been a make-up day for those who missed any final exams. The finals will be rescheduled after classes resume Jan. 5.
"Does this mean that a kid anywhere who doesn't want to take finals can cancel classes by putting something on the Internet?" asked parent Steve Schweitzberger. "But on the other hand, you have to regain respect for authority. Credit the district for making a swift decision to cancel classes."
The new threat renewed the fears of the students who attend this school.
"I knew half the people that were killed so it's bringing everything back," one student said.
Columbine student body President Mike Sheehan told CBS Early Show Anchor Bryant Gumbel he feels very safe at school dspite the threats against security, but wants no more surprises.
"I wish I could see the end. I don't know where it is right now," Sheehan said. "We're hopeful for this day to get past us."
However, Internet expert John Vranesevich felt that the threat made in a chat room geared toward teen-age users was taken too seriously.
"You have to take the threat in the context of where it came," says Vranesevich, whose company, AntiOnline, educates users about computer security.
While he sympathizes with the concerns of Columbine officials, Vranesevich believes a virtual room full of up to 100 teens is an atmosphere of loose banter, kids "just shooting the wind."
"Now that we've tracked down an individual, are we going to start a witch hunt just because he made a comment in an IRC (Internet Relay Chat) room?" he asks.
It has been a tough week in Littleton. Four days earlier, Time magazine revealed videos made by Harris and Klebold.
Meanwhile, a long-planned concert was put on Thursday night to thank those who helped the school through the shooting tragedy last April.
About 4,000 people attended the show in the school's parking lot. The show was intended as a gesture of gratitude to the law enforcement, health care and religious agencies that responded to the shootings.