BANGOR — One of two southern New England men charged with killing three Maine residents last year and then setting fire to a car containing the bodies told investigators that one victim pleaded for her life before being shot.

Randall Daluz, 35, of Brockton, Mass., told detectives that two men were dead when he got into a car with drug dealer Nicholas Sexton of Warwick, R.I., in August 2012 and that he watched Sexton use a derringer handgun to kill a third victim, who was crying and hysterical, according to a state police affidavit filed in Superior Court.

But the affidavit also quoted a former cellmate of Daluz’s as saying he killed the woman to earn Sexton’s trust.

The defense argued Thursday in court for separate trials. Prosecutors argued that since the evidence against both men is the same they should be tried together. The judge did not immediately rule.

Sexton and Daluz were accused of killing the victims in a drug-related dispute. The victims, whose bodies were recovered from a car found burning in Bangor on Aug. 13, 2012, were Daniel Borders, 26, of Hermon; Nicolle Lugdon, 24, of Eddington; and Lucas Tuscano, 28, of Bradford.

Sexton and Daluz came to the Bangor area in Sexton’s rental car to sell drugs, according to the affidavit.

The investigation found that Sexton was angry at Borders for allegedly switching to another source of drugs. A derringer linked to the bullet that killed Lugdon was later retrieved from the muddy bank of the Penobscot River.