The 14-year-old boy was handcuffed and arrested for making the anonymous threat on an Internet message board. A Peoria, Ill., man reported the posting to authorities.
The teen had posted an aerial photograph of the high school and wrote that he was planning to detonate bombs at the school and shoot survivors from the rooftop.
Authorities said the teen was held for a few hours, then released without charges being filed. The teen reportedly has a history of behavioral problems and was looking for attention. They said he had no intention of following through on the threat.
The Associated Press contributed to this report.