CONFIRMED: One 15/16-year-old victim with a gunshot wound. Unknown gender, unknown condition. #ArapahoeHighSchool

— 9NEWS Denver (@9NEWS) December 13, 2013

Via ABC 7 Denver:

Arapahoe County Sheriff Grayson Robinson told CALL7 Investigator John Ferrugia that there has been a shooting at Arapahoe High School.

Robinson believes there are two victims and that the suspect is inside the school.

A 7NEWS viewer said she saw more than 20 police vehicles at the school.A

Another witness told 7NEWS she saw police in riot gear at the scene.

Arapahoe High School is at 2201 East Dry Creek Road in Centennial.

Littleton Public Schools and Elizabeth schools have been placed on lockdown.