When a man shot at police during a traffic stop Monday, officers did not return fire. How do they make that call? Think about it ... someone is firing a gun at you ... how do you decide to reach for your own firearm?

I posed that question to Paul Farnstrom with the Multnomah County Sheriff's Office. He trains officers in the use of force and says no two incidents are ever the same and you can't compare them. In each case, an officer must consider his or her surroundings ... what's in front of and behind the suspect ... they're size ... what type of threat they pose ... and so forth. If there's a danger of hitting a bystander, the gun stays in the holster.

The officer ALSO has to keep in mind what weapon is in play. Deputy Farnstrom says you would NEVER use less lethal force (e.g., a taser or pepper spray) against a gun because you're risking your life at that point. If the suspect is using lethal force, the officer can ONLY choose between lethal force or no force.