Authorities, however, believe the killings are unrelated.
Riccobene, 60, a silver-haired mob associate, formerly of Packer Park in South Philadelphia, was apparently shot through the driver's side window and died of multiple gunshot wounds of the head, according to Camden County Prosecutor Ed Borden.
Borden said Riccobene did not have a gun on him, but declined to say whether a weapon was recovered.
In the past eight months, mobwatchers had spotted the recalcitrant former member of the federal witness protection program in South Philly and South Jersey, in restaurants in Delaware County and had even seen him with his mother the day before he died.
"It was just a matter of time before someone would take a run at him," said one organized crime source.
On Thursday, he had been waiting for someone he obviously trusted - the usual way a mobster meets his demise, according to law enforcement sources.
"He was an empty guy, not popular at all with other criminals," one law source said.
There were enough people out there with motives to kill him.
He had become a "snitch" at a time when the Mafia code of omerta, or silence, still prevailed in the mid-1980s.
He testified in two mob trials and linked dozens of people to mob violence, one of the first mob insiders to do so.
In 1984, he ratted out his half-brother, Harry "the Hunchback" Riccobene, a "made" member of the mob, testifying against him and others in the 1982 murder of mob associate Frank Monte.
Harry Riccobene, a short, wiry, notorious drug trafficker, just shook his head in disbelief during Mario's testimony, according to those who attended. Harry Riccobene is serving a life term in that case.
Only two years earlier, Monte and mobster Raymond "Long John" Martorano, an ally of Nicodemo "Little Nicky" Scarfo had asked Mario to help them set up Harry's killing.
At the time, Mario had tried to protect his half-brother and sided with him in a bloody feud from 1982 to 1984 that split the local mob into two factions, one headed by Harry, the other by Scarfo.
Then, Mario later testified against Martorano in the murder of Roofer's Union leader John McCullough in 1980. Martorano is in prison awaiting a new trial in the McCullough murder.
Mario was not a "made" member of the mob, but was Harry's right-hand man and gofer, picking up money in the Riccobene family's loansharking and gambling operations. He was sentenced to 4 1/2 years in a 1982 federal racketeering and loansharking conviction.
In return for his cooperation, Riccobene entered the witness security section of federal prison in July 1984 to serve a 4 1/2-year sentence for his role in Monte's killing. In December 1988, he was released into the witness protection program.
But he couldn't stand it. He couldn't stay away from the people and places that jeopardized his life. He was on the phone calling home, much to the dismay of authorities. He lasted less than a year.
Riccobene was kicked out of the protection program in October 1989 after violating security on two occasions, according to FBI spokeswoman Linda Vizzi.
"At the time of his death, he was not a protected witness," she added.
Investigators last night were trying to reconstruct Riccobene's last days. He carried a phony driver's license from Charlotte, N.C., listing his address as "187 Rural."
And his family and friends hovered around Mario's mother, Jennie Riccobene, at her ranch-style house under the tall oaks in a section of rural Gloucester County called "Crazy Oaks" in Franklinville.
Relatives and friends stood outside the one-story stone and beige cedar- shingled home which he shared with his mother.
"She's devastated," said a man in a black T-shirt and slacks.
"It's her only son," said a blond-haired woman next to him.
Mario's brother, Robert Riccobene, was killed execution-style Dec. 6, 1983. And Mario's son, Enrico, committed suicide eight days later inside his store on Jeweler's Row because he feared he would be the next mob hit.