Boise, Idaho - The past is quickly closing in on Enrico Ponzo.

The man accused of being a New England mobster who tried to whack his boss then hid out for years in Idaho was placed under the supervision Friday of U.S. marshals who will supervise his return to Boston.

A federal judge also said 42-year-old Enrico Ponzo will remain in custody without bond until he is moved. Marshals declined to say when that would occur.

Ponzo was arrested earlier this week at the home he built in the shadow of the Owyhee Mountains.

Ponzo said at the hearing he had kept his past a secret to protect his family and friends.

"My past is not a very nice thing," he said.

News that he was alive and had been captured surprised many authorities who worked organized crime cases in Boston in the 1990s.

"A lot of people suspected that he might have been a murder victim himself," said detective Lt. Stephen Johnson of the Massachusetts State Police. "He lasted out there for a long time for a fugitive. It's not an easy life."

Authorities say Ponzo fled Boston in 1994 and for at least the past 10 years has been living a quiet, inconspicuous life under an assumed name in Marsing, a farm town west of Boise.

FBI agents had been investigating Ponzo for about a week prior to his arrest Monday.

FBI Special Agent Douglas Hart said authorities were focusing on Ponzo for a warrant issued a decade ago in Massachusetts, not on any current criminal enterprise.

Hart said Monday's search of Ponzo's home yielded 38 firearms, including 18 rifles, one of which was fully automatic, and tens of thousands of rounds of ammunition.

Agents also seized $15,000 in cash and at least 50 books and manuals detailing ways to create aliases and false identification, he said.

Authorities can link Ponzo to Idaho as far back as 2001, when he was cited for a traffic violation.

Ponzo is suspected of fleeing Boston in 1994 to avoid state drug charges.

Three years later he was charged in a 40-count indictment involving 14 others related to organized crime. The charges included trying to kill former mob boss Frank "Cadillac Frank" Salemme.

Ponzo is accused of taking aim at Salemme in 1989 outside an International House of Pancakes in Saugus, Mass.

Salemme was shot in the leg and chest during the attack and survived. Three other alleged members of the Patriarca Family of La Cosa Nostra were killed in the gunfire.

Salemme served several years in prison after being indicted in 1995 on racketeering and other charges.

In 2008, he was sentenced to five more years for lying to authorities investigating FBI connections to organized crime. Authorities now say Salemme is in the federal witness protection program.

Ponzo made his first appearance in federal court in Boise Wednesday, pleading not guilty to the federal charges.

In Idaho, he had been living under the alias of Jeffrey Shaw and was described by friends and neighbors as hardworking, polite and a proud father of two children.

Prosecutors argued Friday that he is a significant flight risk and urged he be kept in custody until arrangements are made to get him back to Massachusetts.

Ponzo's attorney, federal public defender Samuel Rubin, made a case for an alternative custody plan when Ponzo arrives in Boston.

Rubin urged the judge to appoint Ponzo's older sister, Alexandria Divadkar, as a third party custodian, meaning she would take responsibility for her brother and ensure his appearance in court.

Testifying by telephone from her home in Swampscott, Mass., near Boston, Divadkar acknowledged it had been 20 years since she last spoke with her brother.

Still, she said his life in Idaho proved he had turned the corner and deserved a chance to prove he could be trusted.

The testimony was emotional for Ponzo. Calm and casual during the early stages of the hearing, he lowered his head and rubbed his eyes when his sister began answering questions and recounting the deaths of their mother in 1997 and their father several years later.

"It looks like to me that he really did his best to change," she told the judge.

Magistrate Judge Ronald Bush disagreed, saying if Ponzo had changed he would have stepped forward and faced the criminal charges from his past.

Denise Lavoie contributed to this story from Boston