The officer can only act on what he knows-his perception. The force he chooses to use must be reasonable or he faces the consequences.
Case in point-A armed deputy just outside the booking area sees and hears the following:
1. Several louds booms he beleives are gunshots coming from the jail area.
2. Hears a jailer screaming, "He's got a gun, he's got a gun."
3. Jailer runs past the deputy pointing behind her.Deputy draws his gun.
4. Guy comes running around a corner right behind the jailer.
5. Deputy shoots the guy.
Is that a reasonable use of force based on the deputies perception? In that split second would that be an appropriate choice? In that flash of a moment in time would you considerate it reasonable to fire to save your life, the jailers life and everybody else's life in the building?