Dundee-Crown High School was put on lockdown late Friday morning so police could investigate a text message threat about a student planning to take a gun to school, officials said.
The lockdown, however, was called off after the student in question was determined to be off-campus. The teenager believed to have started it all is being questioned by police, officials said.
"He's in custody now; we're still investigating," Carpentersville Police Cmdr. Timothy Bosshart said. "I'm sure he's going to be charged, but I can't release anything until he is."
The school's police liaison officer learned at 11:15 a.m. that a senior had threatened a fellow student via text message, saying he was bringing a gun to school.
"I believe it was a vague threat, that he's going to come back to school with a gun," Bosshart said.
The school was put on lockdown after that, and students were moved to interior classrooms for safety.
Officers began a sweep of the high school, while others tried to find the student who made the threat. Police and school officials said the student made the threat following an altercation with another student Friday morning at the school.
At about noon, police made contact by phone with the student they say sent the threatening message. The student went home and surrendered to police. The police investigation did not indicate there actually was a weapon.
The district took both schools off lockdown at 1 p.m.
An automated phone alert was sent to parents of kids at Dundee-Crown and neighboring Perry Elementary School at 12:30 p.m.
Meri Kirsme of Carpentersville, who has two children at the high school, went there to deliver allergy medicine to her freshman daughter. She was instead greeted by police who said she could not go in. She said she was impressed with the police response -- officers from Gilberts, West Dundee and Carpentersville were highly visible.
"I have no problems about my kids' safety here, I know they're going to be taken care of," she said.