Oct. 31, 2013 at 8:30 AM ET
On Halloween night 20 years ago, actor River Phoenix, 23, collapsed and died outside the Viper Room nightclub in West Hollywood, Calif.
Fans were shocked. Phoenix was well known from both his child star days ("Stand by Me") and his venture into adult roles ("My Own Private Idaho"). An autopsy found high concentrations of cocaine and heroin in his blood, which unnerved fans accustomed to Phoenix's squeaky-clean activist image.
Phoenix's mother wrote in the Los Angeles Times that her son was no drug addict despite the circumstances of his death.
"His friends, co-workers and the rest of our family know that River was not a regular drug user," Heart Phoenix wrote. "We feel that the excitement and energy of the Halloween nightclub and party scene were way beyond his usual experience and control. How many other beautiful young souls, who remain anonymous to us, have died by using drugs recreationally? It is my prayer that River's leaving in this way will focus the attention of the world on how painfully the spirits of his generation are being worn down."
Our slideshow takes a look at more than a dozen entertainers -- comedians, actors, musicians and more -- who died before they reached 40. It's no surprise that many deaths were brought on or more indirectly influenced by substance abuse. But others died in plane and car crashes, other accidents, or of illness. And all of them exited the stage far too soon.