A pivotal scene in the movie calls for Brandon Lee's character, Eric Draven, to enter his apartment to find his girlfriend Shelly being assaulted by a group of thugs. One of the thugs, played by Michael Massee, points a gun at Eric and shoots him the chest.
The gun used in the scene, a .44 Magnum revolver, had previously been used in another scene where a character points it directly at the camera. In close up shots like this, the chambers of a revolver, which will be visible, are filled with dummy rounds so that the gun looks loaded. The dummy cartridges have the gunpowder and primer removed so that they still look real but cannot actually be fired. On the Crow, the production team, which was running behind schedule, chose not to purchase commercially made dummy rounds but rather to modify live ammunition to make dummy rounds. They did so by removing the powder from the rounds, but they forget to remove the primer. At some point, either during the scene or after it, the gun was discharged, setting off the primer and pushing one of the dummy rounds part way down the barrel of the gun.
On the day of Lee's death the weapons master was not on set. Another member of the props department prepared the gun for the scene and apparently did not check to make sure that there was nothing in the barrel. For the assault scene, the gun was loaded with blanks, rounds which contain powder and primer but no bullet. This is done so that the gun can produce a gunshot when fired but will not actually send a bullet flying. When Michael Massee fired the gun in the scene, the gunpowder from blank round caused the bullet lodged in the chamber to be fired at Lee with almost as much force as a live round. Lee was rushed to a hospital, where he died after several hours of surgery.