NEW YORK (CBSNewYork) -- It was a crime that gripped the New York area. Six family members were wiped out in a gruesome mass murder that inspired one of the scariest movies ever made: The Amityville Horror.
Thirty-seven years later a claim that new evidence has been unearthed is raising new questions.
Neighbors told CBS 2's Jennifer McLogan that they remain spooked by the infamous house.
"I wouldn't go in there at night," Anthony Oldham said.
But as terrifying as the movie is, the real-life events that inspired the blockbuster were much more frightening.
"It's a very tragic story," said Amityville resident Peter Stein.
It all unfolded on Nov. 13, 1974, when 23-year-old Ronald DeFeo Jr. used a high-powered rifle to shoot and kill his parents, two younger sisters, and two younger brothers, while his victims lay sleeping in their beds.
DeFeo confessed to the killings, telling police that "the voices from the house made him do it."
Oldham said that the murders were an "open and shut case," but documentary film maker Ryan Katzenbach begs to differ.
"This crime did not happen the way it is commonly accepted," he said.
New evidence suggests that there could have been a second shooter.
"We firmly believe that there was indeed a second gun involved in the commission of the crime," Katzenbach said.
Katzenbach is working on his third documentary about the murders. He insists that he has the documents and the evidence to prove that there was more than one person responsible for the murders.
A team of underwater archeologists, hired by Katzenbach, have found a gun in the canal behind the house.
Aqua Survey's Mark Padover told CBS 2 that "Once we cleaned it off, you could see that there was a trigger and a handle." Padover said that the gun was turned over to a crime lab immediately for a forensic ID.
Katzenbach said that this new evidence confirms a long-standing belief that DeFeo didn't act alone. He needed help to kill six people.
Katzenbach has long questioned the idea that a single person could have committed the crime.
"How could a person walk through a three-story Dutch colonial and shoot six different victims, on two separate levels and no one got out of bed, no one put up a struggle?" Katzenbach said.
Other details about the case, taken together, add up to a second gun and a second shooter, he said. Evidence like a photograph of a pillow case found in a trash can next to the canal.
"We knew that DeFeo had used pillow cases in the cleaning up of the crime scene," said Katzenbach.
After the killing police said that DeFeo used a pillowcase to carry a rifle and other evidence that he took from the house and tossed it all in a storm drain. They found his hand gun holster but no gun. Katzenbach said that the missing gun is the one that his team pulled out of the canal.
Katzenbach claims that other details from the 1974 police report point to the possibility that someone else helped DeFeo kill his family. Eyewitness reports, crime scene photos, and hand written notes all add up to a second gunman, according to Katzenbach.
But Suffolk County Police aren't convinced. They say that only one gun and one shooter killed the family.
"People are very creative and the Internet allows them to pull up items that they think are facts, when in fact, they're not facts," said Detective Lt. Gerard Pelkofsky, Homicide Chief for the Suffolk County Police Department.
Katzenbach maintains that evidence was overlooked once the police found a suspect and got a confession.
"It's a very famous case for Suffolk County. DeFeo has been sitting in prison for 37 years now. To open this up and to chance DeFeo getting a new trial, I just don't think that's the route they want to go," Katzenbach said.
The gun is still being examined, but with decay and a lack of a legible serial number it may be impossible to ever identify.
DeFeo is currently serving six consecutive sentences of 25 years to life. Over the years he has changed his account of the murders numerous times.
For more information pertaining to this case, please click here.
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