"The 40-year-old just joined the University of Maryland police force this summer. He was in training with city police. His training class was using an area with abandoned buildings when his instructor accidentally shot him in the head."
Just in case you are new to firearms the Four Rules are:
Rule One: All Firearms are always loaded at all times.
That means you treat EVERY weapon as loaded, even after you clear it and physically and visually check the chamber. Make that ESPECIALLY after you check the chamber.
Rule Two: Never let the muzzle of the weapon cross anything you are not prepared to destroy or shoot.
That means never point it at anything you are not intending to actually shoot. Firearms are NOT toys. They are tools, and handled improperly they can kill or injure people, animals, vehicles, cars, aircraft you name it.
Rule Three: Keep your finger off the trigger until such time as your sights are on the target.
Keep your boogerhook off the bang switch. Until your sights are on your target your finger belongs OUTSIDE of the triggerguard.
Rule Four: Be sure of your target and what is beyond it.
YOU are responsible for any projectile that comes out of the barrel of your firearm. Telling a police officer "I didn't know the bullet would go through that wall and kill the child on the other side." is a cold comfort for that child's parents. Same thing with shooting outside. If you don't have a proper berm, backstop or hillside to shoot into DON'T SHOOT!
Remember the first and BEST safety of ANY firearm is between your ears. And if you don't understand what that means, you really don't need to be handling a firearm in the first place.