A retired Marine stops a potential killing (they say potential mass shooting, but even if he just stopped a nutter from shooting *one* person, that's plenty heroic) by taking down a gun-waving nutjob *with his bare hands*
When police arrive to take the gun waving nutter into custody for his criminal actions, the retired Marine, thinking he's doing the right thing, informs the police that he's got a concealed handgun license and he's carrying. The problem? The incident happened in Maryland. The heroic Marine is from Virginia. NO reciprocity, and the cops are assholes who arrested the good guy right along with the bad guy. Now the good guy is facing charges and will likely lose his right to carry, even if its a misdemeanor.
Permits / licenses for a *right* are pure bullshit. If a driver license / ID is valid across state lines, then at the very least carry permits should be the same, but carry permits ARE an infringement against a God given, Constitutionally recognized right to begin with.