Arlington Heights police said a school resource officer removed his service weapon while inside a restroom just before dismissal Monday. He realized it was gone moments later.
Officers searched the building, reviewed surveillance video, and called in multiple K-9 units trained to detect weapons, but the gun was never found. A school officials said they received confirmation that the gun is not in the building.
Investigators said only a limited number of people entered that bathroom during the time frame and they're now working to track down who may have taken it.
Classes at the specialized school are canceled Tuesday, with extra police presence expected on campus for the investigation.
Police are urging anyone with information to come forward as they work to recover the missing firearm and determine exactly what happened.