Admitted cocaine trafficker Eugene Coleman (search) was hoping to earn himself a lighter sentence last year when he agreed to cooperate with prosecutors investigating a notorious Philadelphia drug gang. He may have paid a steep price for leniency — steeper than any punishment a judge could impose.

Before dawn on Saturday, someone entered the home where Coleman's family lived, emptied a can of gasoline and started a fire that swept through the two-story building.

Six people in the home died breathing soot and hot ash. The victims included Coleman's mother; her grandsons, age 12 years and 15 months; her 33-year-old niece; the niece's 10-year-old daughter and a 15-year-old family friend.

The killings remain unsolved, but authorities are examining whether they may have been an act of revenge.

Coleman, 27, was identified in court papers in June as being among several alleged gang members who offered to tell all about their drug operation in return for the possibility of more lenient treatment in their own cases.

Based partly on their statements, 27 alleged members of the gang were indicted last spring. In a memorandum to a judge, prosecutors said Coleman had agreed to testify to helping the gang's alleged leader, Kaboni Savage (search), prepare at least 220 pounds of cocaine for sale on the streets.

FBI agents and police investigating Saturday's fire declined to say much about the probe, other than to acknowledge that they are looking into whether the victims' relationship to Coleman made them targets.

They aren't the first witnesses in the case to turn up dead.

In January, one dealer who prosecutors said had repeatedly fed information to the FBI was shot six times on a city street corner.

In February, a man who was to testify against Savage for a 1998 murder case was gunned down in his car. Savage was acquitted of the killing at trial. In a court filing, an FBI agent said authorities believed Savage ordered the witness' murder.

Savage's attorney did not return a phone call Tuesday, but has previously called allegations that his client was rubbing out witnesses "ridiculous," and suggested they may have been fabricated by overzealous law enforcement officers.

Philadelphia Police Commissioner Sylvester Johnson (search) urged anyone with information about the fire to put any fears of retribution aside and tell investigators what they know.

"People in the community are more safe with these people in jail instead of on the street," Johnson said at a news conference. "The public should be totally outraged that six innocent people were killed, burned to death in their own home."

Both Savage and Coleman are being held without bail at a federal detention center in Philadelphia.

Coleman is tentatively scheduled to be sentenced for his role in the drug ring in December. He is also awaiting trial for the murder of a New Jersey man whose body was found in the trunk of a car in Philadelphia last year.

The drug case had been covered intensely by Philadelphia's news media, even before the fire, because of its tangential relationship to a federal public corruption probe.

During the course of the gang investigation, FBI agents said they intercepted several phone calls between dealers and the leader of an influential Philadelphia mosque.

Intrigued, the agents obtained a judge's permission to tap the imam's home telephone, and allegedly recorded him discussing schemes to rig government contracts.

That led to further wiretapping of city officials, and the eventual installation last fall of an FBI listening device in the office of Mayor John F. Street (search).

Street has not been accused of any crime, but prosecutors have charged several of his supporters with corrupt acts, including the city's former treasurer, a mayoral aide, a city council aide, the imam and a lawyer who raised money for the mayor's campaigns.