Heather Michele O'Rourke Born: Heather Michele O'Rourke on 27 December 1975 in Santee, San Diego, California. Died: 1 February 1988, San Diego, California, USA (cardiopulmonary arrest and intestinal stenosis) About her death: She was on medication throughout the filming of her next project, Poltergeist III (1988), and her cheeks were puffy in some scenes. She never complained during filming and did not appear sick to fellow cast members. When filming temporarily stopped in June, Heather and her family went on a road trip from Chicago, to New Orleans, to Orlando and all the way back to Lakeside where they lived at the time. Heather was well until January 31, 1988, Super Bowl Sunday. She was unable to keep anything in her stomach and crawled into bed with her parents that night, saying that she didn't feel well. The next morning, February 1, sitting at the breakfast table, she couldn't swallow her toast or Gatorade. Her mother noticed her fingers were blue and her hands were cold. Kathleen called the doctor's and was getting ready to put her clothes on when Heather fainted on the kitchen floor. When the paramedics came in, Heather insisted that she was "really okay" and was worried about missing school that day. In the ambulance, Heather suffered cardiac arrest and died on the operating table at 2:43 p.m. at the tender age of 12. Of all her achievements, Heather was proudest of being elected student body president of her 5th grade class in 1985.

Just adding to the other answers. Her parents sued her doctor for loss of "future earnings" and claimed that a wrong diagnosis killed her if I recall correctly. Side note, Dominique Dunne who played her older sister was murdered by her boyfriend in 1982.

just a few more things :) fun info as the movies were sead to be cursed During the scene where Robbie (Oliver Robins) is being strangled, the clown's arms became extremely tight and Robbins started to choke. When he screamed out, "I can't breathe!" Steven Spielberg and Tobe Hooper thought that the boy was ad-libbing and just instructed him to look at the camera. When Spielberg saw Robbins's face turning purple, he ran over and removed the clown's arms from Robbins's neck. There is a supposed "Poltergeist Curse" surrounding the three films in the series. Actress Dominique Dunne was murdered by her boyfriend after finishing the first film. Actor Julian Beck died of stomach cancer after shooting the second film. Actress Heather O'Rourke died of a mystery case of intestinal stenosis shortly before completion of the third film. Also, many cast members' careers have suffered after appearing in the films. i think there is more but i have to go at the moment XD