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A 73-year-old man who police believe escaped into a vast New York forest after allegedly gunning down his daughter-in-law seven months ago and was widely believed to be dead, may be alive and on the run, authorities tell FoxNews.com.

Eugene Palmer, of Stony Point, N.Y., is wanted in the Sept. 24 shooting death of his daughter-in-law, Tammy Palmer, in what authorities described as a "cold-blooded" and "premeditated" murder.

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Palmer waited for his 39-year-old daughter-in-law to place her to two children on a school bus before shooting her three times with a bolt action shotgun as she walked up the driveway toward her home, police said. Palmer, a retired part-time park ranger, then fled into Harriman State Park -- a 46,000-acre stretch of woodland filled with caves, root cellars and abandoned mine shafts that borders the man's home, according to police.

While Palmer's sons claim their father -- a severe diabetic -- died in the woods, authorities tell FoxNews.com they suspect he escaped the park, and they've recently launched an international manhunt through Interpol to track him down.

"I don't believe he's in that park. He's been out of that park since September," said Sgt. George Lutz of the Haverstraw Police Department. "We are proactively looking for Mr. Palmer using every resource we have."

"We believe that he has weapons. We consider him to be armed and dangerous," Lutz said of Palmer, who has been charged with murder.

Lutz said Palmer drove to his niece's home shortly after the alleged killing and confessed to the crime. He also left money with his sister to pay his taxes and told the woman to give him an hour before contacting authorities, according to Lutz.

Hours after the shooting, police found Palmer's abandoned pickup truck on an old fire road about a quarter mile into the park. An extensive manhunt ensued, using air and foot patrols as well as bloodhounds. A "hit" was detected by one of the dogs, leading police to a campsite within the park, but it remains unclear whether the scent belonged to Palmer.

The Haverstraw Police Department also requested assistance from state and federal law enforcement, including the FBI. They found no conclusive evidence of Palmer in the park, other than his truck parked deep into the woods.

"He knows this park like the back of his hand," Lutz said of Palmer, known to locals as a so-called "Mountain Man," well-versed in the many trails and caves inside the park.

Police say Palmer became increasingly enraged over "domestic issues" between Tammy and her estranged husband, Eugene's son, John. Tammy Palmer had reportedly filed an order of protection against her husband, meaning John could not step foot on the 3 1/2 acres of land where both Tammy and Eugene lived in homes close to each another.

"That's what led up to his actions of that day," Lutz said of the motive.

Palmer's two sons, John and Clarence, did not respond to requests for an interview. According to the Journal News, the family claims Palmer acted out of character and snapped that morning, suggesting the alleged murder was not planned in advance. They told the newspaper Palmer fled the scene in his slippers, leaving his breakfast uneaten on his kitchen table.

"If the police didn't botch the hunt in the beginning, my father's remains would be where they belong," Clarence Palmer told the newspaper. "They were afraid of going into the woods; afraid of a man with a shotgun, supposedly. If he wanted to be found, he would have finished himself off here. He went into the woods. I think he fell into a diabetic coma."

Lutz appeared skeptical of such claims, telling FoxNews.com, "I don't know how you'd know what somebody was wearing unless you were actually looking at them."

"He waited for his grandchildren to get on the bus before executing their mother," he said. "That's pretty cold-blooded."

Lutz said he cannot rule out the possibility that Palmer had assistance in his getaway. He said detectives have theories about where he might be, but declined to elaborate.

A shotgun was recently found by the family, buried under leaves near Palmer's home, but Lutz said he does not know if that was the weapon used to kill Tammy Palmer. He said Eugene Palmer, an avid hunter, owned several shotguns.