Study of cop-killers
Here's a summary of a study of killers of law enforcement officers. Of relevance here: only one of the 40 studied bought a gun legally. "Researcher Davis, in a presentation and discussion for the International Assn. of Chiefs of Police, noted that none of the attackers interviewed was "hindered by any law--federal, state or local--that has ever been established to prevent gun ownership. They just laughed at gun laws.""
The cop-killers boasted of being better shots and more practiced that the LEOs they fired on. 40% had been in gunfights before the one with the officer.
Interesting cues for LEOs:
None used a holster, they generally tucked the gun into their waistband. As a result, they have to feel it from time to time to make sure it's in place, and when running, have to keep a hand on it. Both should be clues that the suspect is armed.
40% carried a backup gun, at least on occasions.
Female officers are more thorough at searches of suspects, but are more likely to overlook the fact that females with the suspect may also be armed.
The gang-bangers' style is to avoid using sights, get the first shot in, and just fire in the general direction. The first hit is all-important, because if the other person goes down, they can always walk over and finish him off. (For LEOs this would underscore the FBI program I've heard about, something like just because you're hit doesn't mean you're dead. Most people hit just collapse, when they actually could continue the fight. In this setting, keeping up the fight means surviving, since the gang-banger doesn't plan on taking prisoners).