It was, perhaps, shocking enough when the authorities announced last week that after 12 years of fruitless investigation they had arrested a man in connection with the gruesome murder of a 19-year-old Brooklyn man whose expertly dismembered body was discovered spread in plastic bags in a subway station and a trash recycling plant.

But in making the announcement on Wednesday afternoon, the police and prosecutors revealed another tantalizing tidbit: The suspect had also been charged with a second cold-case murder — that of a 17-year-old girl whose remains had been found in an alley inside laundry bags a year before the young man’s body was discovered.

Unlike the killing of Rashawn Brazell, which garnered widespread coverage in the media, including three episodes of “America’s Most Wanted” on television, the long-mysterious earlier death went essentially unmentioned for more than a decade. The naked body of the girl, Sharabia Thomas, had been discovered, folded in half and stuffed inside the bags, in Bushwick, Brooklyn, 13 years ago, bruised and bearing marks suggesting that she had been tied up before she died.