A document accidentally posted on the Nassau County DA’s Web site offers a new version of the friendly-fire shooting death of a federal agent during a New Year’s Eve robbery of a pharmacy.

The altered chronology, which is based on an interview with the pharmacist, differs from an account offered by a lawyer for the retired police lieutenant who fired the fatal shot.

The pharmacist says the former Nassau County cop, who ran to the scene when he heard reports of a robbery in progress, shot once when he came upon a skirmish between a robbery suspect and a Bureau of Alcohol, Tobacco, Firearms and Explosives agent on the sidewalk outside.

That shot killed ATF agent John Capano, who was a customer in the Seaford pharmacy and had chased the robbery suspect outside.

The lieutenant’s lawyer, Brian Davis, has said that his client, Christopher Geraghty, opened fire only after a shot whizzed past his head.

Davis said Geraghty thought the shot came from the robbery suspect.

The DA issued a statement saying, “This interview represents just one of the many perspectives on the Seaford tragedy, and no conclusion should be drawn from it.’’