The way I see it...
I'm a resident general surgeon and am soon to be trauma chief resident at a level I center.
If a penetrating injury is instantly lethal--that is the person drops without a pulse, don't bother getting your hands dirty, its over.
If a penetrating injury quickly causes some sort of cardiac or pulmonary instability (this is the person who will lose a blood pressure or develop respiratory failure within minutes) the only life saving procedures one could usually offer can only be performed at a hospital and usually in the operating room (with the exception of a temporizing tourniquet on a bleeding extremity). Similarly, if someone has a severe head injury and is unconscious but with pulse, they need intervention. In the unstable population, the "platinum 10 minutes" and "golden hour" are often used to look at how critical time is managed.
The last category are those who have an injury that might be life threatening, but who are stable (i.e. bowel injury). These folks may have lethal or non-lethal injuries, but are, lets say, not going to die within the hour (think Civil War). Their outcome is likely not dependent on initial first-aid. In fact, this is the person you might consider a persistent threat.
My point is simple. If someone has a life-threatening injury, your priority is to call 911 ASAP. Even EMS is not designed to 'save' these people, but rather to get them to a trauma center within 10 minutes, and provide as much ancillary intervention as possible along the way (I used to be an EMT for 4 years, so I understand this from both perspectives). Unless, you can place chest tubes, transfuse blood, crack a chest, or open an abdomen in your living room, any at-home intervention is most likely futile--with the rare exception (i.e. a man faints from the sound of your gunfire and falls unconscious, face-first into your dog's water bowl).
CPR is <5% effective in all patients brought in from the field, and probably 99% of those with penetrating trauma, requiring CPR, will die. If a person loses pulse from GSW "en route", we open their left chest in the ER, clamp the aorta and perform manual compressions. If CPR was in progress since the time they were picke up, I just pronounce them.
I hope this helps. Bottom line is that no amount of care or level of care administered short of a trauma center will be seen as having a role in the person's overall outcome (being that such lethal injuries are virtually all surgical emergencies), ONLY the timeliness in which the person notified the authorities and assisted in the efficiency of that transfer. Lastly, practically no heroic attempt to save a victim of gunshot is worth exposure to hepatitis, HIV, or swine flu
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