At 1:50 p.m., less than two hours after the incident began, police said the shooter, whose identity they knew but would not release, was dead by an apparent self-inflicted gunshot wound.
The suspect was a student at the school, police said. He reportedly came into the school with the intent to confront a teacher, who was informed and able to escape the school safely.
One student, a 15- or 16-year-old had been admitted to Littleton High School with gunshot wounds in serious condition. His identity was not released, but he was reportedly wounded when he confronted the gunman.
Another student was found with a minor injury inside the school, but police said they could not be certain the wound was caused by a shooting.
All Littleton Public Schools and Cherry Creek High School were on lockdown Friday afternoon, but officials said the lockdown was a precaution.