I heard this story in my 7th grade English class 6 years ago, and was fascinated with it, and still am today.
If you don't know anything about the history of the house on 112 Ocean Avenue, in the quaint little town of Amityville, let me enlighten you.

The house in 1974 with the DeFeo "High Hopes" sign and its sinister eye-shaped windows.
The DeFeo Murders
The DeFeo family was looking for a new life away from Brooklyn and looked to a quiet little town called Amityville on the New England coast. They posted a sign at the front "High Hopes" that represented their attitude toward a life anew in this town.
However, the family did anything but get better. Ronald "Butch" DeFeo and his father fought constantly, and one night Butch got so tired of his father fighting with his sister that he grabbed his .35 rifle and held it up to his father's head and pulled the trigger. Lucky for him, nothing came out....that night.
The family's faith in christianity was not helping either, and things just got worse. But on the cold morning of November 13, 1974,at about 1:00-3:00 A.M., the fighting would stop forever.
The early evening of November 13, Butch ran into his friend's bar and screamed that his parents were shot in his house, and demanded that his bartender friend come along as well. When they got there they discovered the bodies of Butch's parents and two sisters Dawn and Allison.
9-1-1 received a call from the distressed bartender. "Everyone's.... Everyone's dead!"
Late that night, the police uncovered a horrific crime scene. All six of the DeFeo family members excluding Butch had been found lying dead face-down in their beds, all shot in the back apparently while slumbering.
This puzzled police in that they were all apparently face down at the time of death, and noone woke up from the gunshots. The gun used was an unsilenced .35 rifle which could be heard by neighbors, but noone heard it.
Ronald "Butch" DeFeo Jr. was suspected and convicted immediately of the murders. He claimed to have heard voices telling him to kill his family members, though now he claims that his oldest sister Dawn, wanted to kill their parents, but when he saw that Dawn killed their siblings as well, he knocked her out over her bed and killed her. "unburned" gun powder was found on her gown and other substantial evidence was found, indicating that this story could be true. He is serving 6 life sentences, and has not been approved for parole.
The Lutz's Move In: Exploitation of a Tragedy or True Story?

George and Kathy Lutz
George and Kathy Lutz moved into the house on 112 in 1975, aware that murders had occurred 13 month ago, but they weren't bothered by this. 28 days later, however, they left the house claiming that they were plagued by terrifying paranormal experiences.
They claimed to have seen flies gathering in the window of the DeFeo brothers' bedroom, slime oozing from the walls at certain times, black oil-like substance overflowing toilets, crucifixes turning upside down, and a pig named Jodie with red eyes that talked to their youngest daughter telling her to stay and play with her forever.
George Lutz claims to have awoken at around 3:15 A.M.(when the murders occurred), and Kathy claimed to have had nightmares about Louise DeFeo, Butch's mother. They also claim to have found a red room behind a wall under the basement staircase and saw an apparition of Ronald DeFeo Jr.
After they had enough, they left all of their possessions untouched in the house. Of course they'd never need them anyway, considering they'd make millions of bucks on the story.
They took their story to acclaimed author Jay Anson, and he made their story known nationwide in 1979. Soon after, a movie was made with James Brolin based on the book. The Lutz's story was known by all.
There have been many debates as to whether this story is true, but many believe it to be a hoax in an attempt to avoid mortgage payments or to simply make money off of the DeFeo's murder story.
True Story or hoax? You decide.
Puzzling evidence and photos
Paranormal experts went to the house in 1976 to investigate the house after the Lutz family moved out. They set up a camera at the second floor landing that night that would take pictures at certain times and noone was at the house at the time. None of the photos showed anything, except this one:
A figure of a boy was seen at the staircase, peaking over the rail with glowing eyes. The boy seems to resemble the youngest boy killed in the house the night of the DeFeo murders.

Ghost boy close-up.

Early photo of the DeFeo family. (back from left to right) John, Allison, Marc, (front) Dawn and Ronald Jr.
A Seventh body?
Other evidence that is pretty weird is that a photo of a possibly 7th body was found in a roll of crime scene photos taken at the murders. A photo of a body laying in a bed in what appears to be the basement of the house(due to the fake wood paneling on the walls) was found, though this may just be Dawn DeFeo's body repositioned in the basement bed. This may have to do with police being seen taking a garbage bag filled with something large back into the house. Either way, this may support evidence of police tampering with the crime scene.
Info and pics about the seventh body can be found here:
http://www.amityvillemurders.com/seventh.html
and crime scene photos on the night after the murders can be seen here:
http://www.amityvillemurders.com/csgallery/index.html
The DeFeo portraits:

Ronald "Butch" DeFeo, 24, and his father Ronald Sr. who would've turned 44 a few days after he was murdered.

Louise DeFeo, 43.

Allison DeFeo, 13, and Dawn, 18.

Marc DeFeo, 12, with his arm around little John-Matthew, 9.
This story continues to fascinate many and goes on to be one of the most notorious murder and ghost stories in America, and a remake of the Amityville movie was made in 2005 that changes a lot of the plot around. Jodie in the movie was one of the DeFeos killed, and the house is bigger and more isolated from the rest of the neighborhood, unlike the real house.
3 families have lived in the house since the Lutz family moved out, and noone has claimed to have any disturbances whatsoever, except for curious tourists purched outside their home and destructive tourists in the early 80s.
The house as it appears today:
A 5 part documentary on the Real Amityville Horror:
Part 1:
Part 2:
Part 3:
Part 4:
Part 5: