A report of a gun near campus prompted West High School's principal to send an alert to parents.
The incident happened at about 3:30 Wednesday afternoon. As a precaution, students were moved to the front lobby of the school.
Knoxville police say they found a car matching the description off campus. Officers did find a gun in the car.
Police sited an 18-year-old suspect with unlawful possession of a weapon and possession of marijuana.