An aging hit man once used as an enforcer by mob boss John Gotti was convicted on Tuesday in the cold-blooded slayings of four people, including a security guard gunned down during an armored car heist in 1990.

A federal jury deliberated over four days in Brooklyn before reaching the guilty verdict against 62-year-old Charles Carneglia. The decision followed a six-week trial that debuted a key Mafia turncoat also expected to testify against Gotti's son.

Jurors acquitted Carneglia of conspiracy in a fifth slaying, which claimed a court officer in 1976. They said they ended their deliberations undecided about a related murder count.

Prosecutors had portrayed Carneglia as a feared Gambino organized crime family soldier who was eager to please his superiors. In one instance — an ambush in the World Trade Center parking lot — he pumped four bullets into a man who ignored an invitation by the elder Gotti to a social club in 1990.

"The defendant's value to the Gambino family is he's a killer," Assistant U.S. Attorney Evan Norris said during closing arguments. "He excelled at intimidation and violence."

Defense attorneys insisted their client was a mob misfit who drank too much to ever be a reliable assassin. He even broke the rules by growing a bushy beard — his "personal way of defying the mob," said one of the lawyers, Curtis Farber.

Carneglia was arrested last year in what authorities described as one of the largest roundups ever of suspected members and associates of a New York organized crime family. Since then, 60 of the defendants have pleaded guilty to lesser charges, and one case was dropped.

In a separate case in Manhattan, John "Junior" Gotti has pleaded not guilty to charges alleging he was involved in three slayings in the late 1980s and early 1990s. He also is charged with possessing and trafficking cocaine.

Gotti's childhood friend and self-described "rat," John Alite, has been cooperating as part of a plea deal and is expected to testify against the Gambino scion later this year. He testified at Carneglia's trial that the younger Gotti — who rose through the ranks while his famous father ruled the New York mob in the 1980s and '90s — organized the World Trade Center hit.

"It was his first job as a captain, and he wanted to get it right," the witness said. The result left Gotti "elated," he added.

Besides the parking lot ambush, Carneglia was convicted in the killing of Jose Delgado Rivera, a 57-year-old security guard who was shot in the back during the armored car holdup at John F. Kennedy International airport in 1990. The two other murder convictions involved a rival mobster stabbed in 1977 during a fight outside a diner and a Gambino associate killed in 1983 during an argument with Carneglia over money.

Prosecutors had alleged that Carneglia shot the court officer to keep him from testifying in a 1976 weapon possession case, then bragged about the slaying to fellow mobsters.

The case produced one of the gorier allegations to emerge recently in mob lore: that the body of John Favara — a neighbor killed for accidentally running over the elder Gotti's 12-year-old son — was dissolved in a vat of acid. Carneglia wasn't charged in the killing, but jurors were allowed to hear testimony that he was involved in disposing of bodies.

Carneglia faces a possible life term at sentencing on June 22.