The former hit man for a Boston crime family may soon see his sordid life story on the big screen, "GoodFellas"-style, after selling the rights to a Hollywood movie producer -- and the law enforcement agent who helped him cop a plea is not happy with the money deal.

John V. Martorano pleaded guilty in 1999 to killing 20 people in exchange for becoming a government witness. Now he's sold the rights to his mob tale for an undisclosed sum to Graham King of GK Films in Santa Monica, Calif.

"I'm not happy with it at all," said Thomas Foley, the retired Massachusetts State Police colonel who led the investigation that exposed corruption between law enforcement and the Boston mob. "That wasn’t the intention when we went into an agreement with him, that he was going to benefit from the activities he was involved in all those years."

Martorano worked with the Winter Hill Gang, a notorious family lead by James "Whitey" Bulger and Stephen "The Rifleman" Flemmi. Nicknamed "The Executioner," Martorano admitted to federal authorities that he'd killed 20 people after he learned Bulger and Flemmi were FBI informants. Bulger is currently on the FBI's Ten Most Wanted List, and Flemmi is jailed for life.

In September, Martorano was a key U.S. government witness against crooked FBI agent John Connolly, who tipped off Bulger and Flemmi that a gambling executive was going to implicate them in other crimes, thus ensuring the executive's murder. Connolly's life story loosely made it to the big screen as Martin Scorsese's Oscar-winning movie "The Departed."

King told Variety, which broke news of the deal on Sunday, that Martorano's life "will be a fascinating story to tell the world."

"When I first met John, I was struck by his unyielding sense of loyalty to those close to him," King told the trade magazine.

King, through his publicist, did not immediately return calls or e-mail for comment.

Massachusetts State Rep. Peter J. Koutoujian, D.-Waltham, a former prosecutor, hopes Martorano's deal will renew interest in a bill he's introduced to stop criminals from profiting from their crimes in the commonwealth.

"He was on the street and he’s acknowledged 20 murders and now he stands to make a small fortune off of this legacy," Koutoujian told FOXNews.com. "I also worry as we sell these stories and we sell this murderabilia, are we creating a farm team for sociopaths?"

Koutoujian's bill is modeled after similar laws in 40 other states.

"I'm not sure you can stop someone from speaking, but you can stop them from profiting from crime," he said. "We teach our children that crime doesn’t pay, yet here are perfect examples of these offenses to human dignity."

Martorano, meanwhile, is back in Boston after serving 12 years in jail. His testimony helped convict Connolly of murder, helped solve some 50 other murders, and led police to six missing mob victims.

"We didn’t want to give a pass to a mass murderer," Foley said. "But really, when you come down to it, it was the only deal we had."

Other co-defendants in the Winter Hill Gang cases have sold their story, angering officials who exposed their guilt and the dismay of the victims' families, who haven't benefited from the deals. "We've made it plain how we feel about it," Foley said. "It's wrong."

He added: "This guy ought to be happy he's just out on the street right now instead of spending the rest of his life in jail or in the electric chair."

Click here to read about the movie deal at Variety.com.