Cause of death: heart attack
River Jude Phoenix (né Bottom; August 23, 1970 – October 31, 1993) was an American actor. Phoenix was known as a teen actor before taking on leading roles in critically acclaimed films. He received numerous accolades including the Volpi Cup and the Independent Spirit Award as well as nominations for an Academy Award, and Golden Globe Award.
Phoenix grew up in an itinerant family, as the older brother of Rain Phoenix, Joaquin Phoenix, Liberty Phoenix, and Summer Phoenix. He began his acting career at age 10 in television commercials. His early film roles include Explorers (1985), Stand by Me (1986), and The Mosquito Coast (1986). Phoenix made a transition into more adult-oriented roles earning a nomination for the Academy Award for Best Supporting Actor for his role in the Sidney Lumet drama Running on Empty (1988). He earned the Volpi Cup for Best Actor and the Independent Spirit Award for Best Male Lead for his performance as Michael Waters, a gay hustler in search of his estranged mother in the Gus Van Sant drama My Own Private Idaho (1991).
Phoenix died at age 23 from combined drug intoxication in West Hollywood in the early hours of Halloween, 1993, having overdosed on cocaine and heroin (a mixture commonly known as speedball) at The Viper Room.
Source : Wikipedia