A little morbid curiosity here.
You come upon a fully fire involved car with a conscious driver trapped inside and no way to extricate him. You have a firearm. Would you put the driver out of his misery?
From a personal moral belief, normally I would, but the laws being what they are, from a practical standpoint, I would have to let the unfortunate victim scream to death.
The only merciful alternative would be to try and shoot the restraining piece of wreckage in order to free the individual, accidentally miss and hit him in the head. Juries might understand such an accidental shot.
Bountyhunter