The police were told by the parents who were present that the gun was a pellet gun. Also, the parents were refused when they ask to talk to him. Murdered is the only word for what happened.
The police were told it might be a pellet gun. The police had no way to know for sure. When the kidnapper pointed the gun at the officer had no choice but to protect himself.
What good would it have been to let the parents talk to him. They are the ones that raised a kid that will bring a gun to school and kidnap and threaten other students. Great parents, great kid.