No one was injured but a student was taken into custody.
Officials say a fight broke out between two boys inside the school. Things then escalated quickly. Police say one of the students received a text message threat that the other student involved in the fight planned to bring a gun to campus.
School officials acted immediately and announced they were going into lockdown.
"We were sitting in our study hall classes and a code red comes on and they said this is not a drill and everyone started freaking out," said senior Devon West. "I almost started crying."
Police arrived and did a sweep of the entire school, searching for the student who made the threat.
"I just remember a bunch of cops coming in with guns. Everybody was real scared," said West.
By noon, police got in contact with the student.
"We did locate him at his house where he surrendered to us," said Michael Kilbourne, acting chief, Carpentersville Police Dept.
Authorities didn't find a weapon in the school or the 17-year-old suspect's house.
The school was on lockdown until about 1 p.m.
"Obviously nothing was a real threat because we're safe, we're in school," said senior Rebecca Libricz.
Police have not released the suspect's name yet because he has not been charged.