As reported by Variety on March 31st, 1993, Brandon Lee was killed by gunfire on the set of The Crow. It was reported that a bullet had gone through his abdomen and become lodged in his spine. 

How could this happen? First of all, it's important to recognize that when Lee was shot, it was during the final weeks of filming The Crow. The film's weapons specialist had already left, according to Entertainment Weekly, but the crew still needed to film the pivotal shot of Lee's character being murdered. This was simple enough (or so it seemed): when Lee entered the set, holding grocery bags, actor Michael Massee would come at him using a prop gun, loaded with a blank, and fire it at Lee. Meanwhile, Lee would detonate a miniature explosive, or "squib," within the grocery bags he was carrying, to create the appearance of gunfire ripping through the bag and killing him. 

At first, the sequence seemed to have gone smoothly: Massee shot, the bags burst, and Lee went down. Moments afterward, though, the crew discovered blood pouring from Lee's abdomen. In a horrifying twist of fate, a real bullet — rather than a blank — had become lodged in the prop gun, and fired into Lee's body. Why? Simple negligence, according to the Chicago Tribune, as it was speculated that the film's "dummy bullets" were probably made in a rush, without proper safety precautions.

Once the injury was discovered, Lee was rushed to the emergency room, given blood transfusions, and operated on. Unfortunately, none of this was enough, and Lee died from his wounds... just a few weeks before he was set to marry his fiancee, Eliza Hutton, according to Inside Edition. To date, this horrible accident remains one of Hollywood's greatest tragedies.