See my remarks last week relating an explanation from BIL who is a cop; the theory is that shooting someone in the head, specifically towards the lower part of the brain, cuts the route for a nerve impulse to detonate the bomb/pull the trigger before synapses can fire and the impulse can make it out of the brain. And shooting them in the chest could trigger the detonator, usually some kind of blasting cap or oversize fire cracker.
Some obvious problems with this; cops are taught to shoot at body mass, ie. the chest, so they have to overcome a reflexive response, and anyone with any experience handling a gun will tell you getting off a head shot in a high stress situation is difficult at best. Of course if they're pinned to the floor and you're point blank, it's a whole 'nuther story. And if the bomb is on a timer shooting the carrier won't accomplish a thing, only make it easier to drag their body somewhere to detonate/defuse the thing. Dead man triggers are annother story but aren't popular or useful as they can misfire, like if the person sneezes/trips, whatever.
Just reporting what I was told, didn't say I believe it.
PC
N P Childs
'I'm Mister Bad Example, the stranger in the dirt, I like to have a good time and I don't care who gets hurt'.
-Mr. Bad Example, W Zevon