The shooter at Reynolds high school in Troutdale, Oregon has been confirmed dead by local sheriff's office.
The gunman, who was allegedly dressed in all black with an AR-15, vest and helmet, was cornered in a bathroom by officers. A statement by officials confirmed that the the situation was "stabilised" and the shooter "confirmed deceased".
No confirmation of injuries or victims have been reported.
Sixty police officials and sheriff's units were reportedly at the scene where an active shooter is operating, Multnomah County Sheriff has confirmed.
Troutdale is situated 16 miles east of Portland. The last day of school was scheduled for Wednesday.
Live feed from the scene showed students being escorted across the school ground.