"The victim was accosted, without provocation, and our investigation has shown that he defended himself while attempting to retrieve his property," the Queens DA said.

What began as a group robbery ended in a homicide aboard a subway train. Prosecutors have provided a rare look into the district attorney’s decision not to charge a man in the fatal stabbing, saying surveillance video shows the victim acted in self-defense.

A homeless man who fatally stabbed one of several assailants who tried to rob him on a 7 train in Queens last month won’t be charged—but the surviving men who tried to rob him will be, prosecutors announced Wednesday.