DiNardo, now 20, made those claims while confessing to his role in the four deaths, sources said.
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However, Philadelphia police say that while they are aware of that reported claims, they are not yet able to link him to any killings in the city.
RAW VIDEO: Commissioner Ross
Commissioner Richard Ross spoke to Action News on Tuesday morning. He said the department would be "remiss" if they didn't investigate.
"We have some work to do, because our homicide detectives haven't had an opportunity to speak to him directly," Ross said. "In order for us to lend any credence to that we have to talk to him directly, which we will do if we get that opportunity. I'm sure we will."
"When you're dealing with someone who's pathological like that, you don't know where they're coming from," Ross said.
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For now, Ross said, investigators will continue to look through their files to see if anything DiNardo mentioned matches up.
But, Ross said, the task is proving to be difficult because they do not have dates, times or exact locations.
He said all investigators have to go on for the moment is, "A nickname he threw out in one case, and an indication about a job that happened in a basement involving a female in another."
The Bucks County district attorney declined to comment beyond court papers released last week, which don't mention the Philadelphia claims.
Police found the missing men's remains on a farm in Solebury Township last week.
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The Bucks County prosecutor said the remains of 22-year-old Mark Sturgis, 21-year-old Tom Meo and 19-year-old Dean Finocchiaro were found buried 12-feet-deep in a common grave.
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The remains of 19-year-old Jimi Patrick were recovered from a separate location.
DiNardo is charged in all four killings, which took place on a farm owned by his parents.
His cousin, Sean Kratz, is charged in the killings of the three men who were found in the same grave. All four were shot and least three set afire.
Video: 2 cousins facing charges over 4 Bucks County killings
According to court papers, DiNardo, 20, who graduated from a Catholic prep school two years ago, said he killed Patrick, a former schoolmate, when he arrived with $800 to buy $8,000 worth of marijuana. He said he shot another man in the back as he tried to run away.
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DiNardo pinned one of the deaths on Kratz, 20, although Kratz told police that DiNardo shot all four.
The only motive disclosed by investigators was that DiNardo said he wanted to set the victims up when they went to the farm to buy marijuana. One man vanished July 5, and the others vanished two days later.
DiNardo told police where to find Patrick, and agreed to plead guilty to four counts of first-degree murder. In exchange, he will be spared the death penalty.
Video: TIMELINE: Murder of 4 men in Bucks County, Pa.
Meanwhile, the family of Mark Sturgis has hired a law firm to look into whether anyone else should be held responsible for what happened on the Solebury farm.
"We are going to look under every rock and every stone until we figure out whether there are others responsible for these senseless deaths," said attorney Robert Ross.
Specifically, they want to know if DiNardo's mental health problems were dealt with appropriately and, given his medical history, how DiNardo gained access to the four guns listed in court papers.
"We're also going to look at whether there were any prior activities on that property, or any other property, and whether any such prior activities give rise to a civil claim of any type," Ross said.
A preliminary hearing for DiNardo and Kratz that had been scheduled for July 31 has been postponed to September 7.
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