Former Mafia hit man Salvatore "Sammy the Bull" Gravano, who was charged while behind bars with ordering the murder of a police detective in Bergen County, has been released early from federal prison after serving most of a 20-year sentence for drug-related convictions in Arizona and New York, his attorney said.

This undated photo provided by the Arizona Department of Corrections shows Salvatore "Sammy the Bull" Gravano.

The New Jersey case was dropped after the killer of Det. Peter Calabro - shot near his home in Upper Saddle River in 1980 - died before he could give evidence at the much-anticipated trial.

Calabro, an officer with the Queens auto theft unit, was identified by law enforcement officers after his death as one of five former New York City officers who sold confidential information to the Gambino crime family.

Richard "The Iceman" Kukinski, a Jersey City native, was scheduled to be the star witness after telling an HBO documentary that Gravano hired him to shoot the Calabro.

But before he could testify, Kukinski died in state prison after claiming to have killed more than 100 people. He was serving life sentences for two murders when he died in St. Francis Hospital in Trenton in March 2006.

Gravano's attorney at the time denied his client had any involvement in the Calabro murder.

Gravano's current attorney Thomas Farinella said his 72-year-old client was released Monday, but wouldn't disclose where Gravano served his time or where he plans to live now that he's a free man.

"He's very upbeat, very positive," Farinella said from his New York office. "It's been 17 1/2 years. A lot has changed. It takes a little bit of getting used to. He's trying to figure out what he wants to do and he's in no hurry."

Arizona Department of Corrections officials said Gravano got released from the state prison system last year, but was incarcerated federally until recently.

Authorities said Gravano will be on federal parole for the rest of his life.

Gravano was a former underboss for the Gambino crime family and confessed to involvement in 19 murders.

He later became a government informant in 1991 and helped bring down 39 mobsters, including the family's boss John Gotti by testifying against him.

Gravano got a five-year prison sentence in a plea agreement and moved to Arizona in 1994 under the federal witness protection program.

He left the program the following year, began giving television and magazine interviews, wrote the book "Underboss" in 1997 and was involved in an Italian restaurant and swimming pool installation company in the Phoenix area.

Gravano was arrested in 2000 along with his wife, daughter and son in connection with an Ecstacy trafficking ring in Arizona that authorities said made them about $500,000 per week.

He was accused of buying 40,000 Ecstacy pills from a drug gang in New York.

Gravano pleaded guilty to drug trafficking charges in Arizona and New York in 2001 and was sentenced to 20 years in prison with an expected release date of March 8, 2019.

Farinella said Gravano "was a model inmate" while imprisoned and "did things to improve himself in various programs without any issues."

The Associated Press contributed to this report.