Film Theory: The Legend Behind the Poltergeist Film

In the year 1982, the film Poltergeist was released and had a huge sucess ever since. If you want to see a horror film classic, then this is the movie. But I'm not going to talk about the film, instead, I'm going to talk about what happened inside the filming production and the strange and scary things that happened to some of its stars.
To do this, I do have to explain a little of what the film is about. In a very short summary, Poltergeist is a about a family that lived in a house that was hunted by ghosts and spirits, this was because the house was built under a graveyard. In a scene of the film, we can see the mother who was trying to save her sons, being in a pool full of mud and skeletons. What they told her after the shot was that, those skeletons were real and that they were dug out from a cementery nearby, because of this happening all the strange things.
On another scene, we can see the son being attacked by a clown, during the one shot, the director saw that the boy was turning blue and that the machine didnt let go of his neck. With a group of people, they released him just in time.
The oldest daughter of them, actress Dominique Dunne, was with a friend of her rehearsing for a new role and, her ex boyfriend entered in her house and choke her to death, killing her in front of her actor friend. The ex-boyfriend was sent to prison.
But what was most strange was the death of the little daughter, who was the reason in the movie why the ghosts hunted the house. Heather O'Rourke died of an illness that claimed her life just months after finishing the film Poltergeist III. The cause is said to be a strange disease that affected her during filming.
Along this and another small facts, people from the world of ghosts and paranormal things have said that Poltergeist is a bewitched film and that the death of the actors in it are no coincidence. But, WHAT DO YOU THINK ABOUT IT?