Operation Crew Cut, a push by the NYPD to curb violence among the city's youth, has lowered the homicide rate among 13 to 21-year-olds by more than half, Police Commissioner Ray Kelly announced at press conference today. But while Crew Cut is generally geared toward protecting "young minority men," it seems that violence among young women and girls is increasing—though police aren't sure why.

Crew Cut, which involves a combination of social media sleuthing and increased foot patrols, has so far resulted in 25 investigations and the indictment of 400 "crew members"—loose affiliations that are usually oriented by neighborhood or housing complex.

NYPD data shows that 43 people in the 13 to 21 age range have been killed this year, compared to 87 over the same period last year. Of the 20 people indicted for those murders, seven have been female, an unprecedented figure: "We haven’t seen that large a number previously," Kelly said.

One such instance involved a 13-year-old girl getting stabbed with an ice pick in the Marcus Garvey houses in Brownsville, after she refused to cooperate with three other girls who were members of a crew called Addicted to Cash, or ATC. Police say the girls wanted the victim to locate a rival in another development.

In another case, a .22 caliber revolver was found in the purse of 14-year-old "Pretty Diana," also a member of ATC. She was caught along with two 18-year-old sisters, who have previously been charged with murder. "Detectives have found that girl on girl crime by crew members is vicious and growing more dangerous," Kelly said. The ATC crew even has its own "girls only" component, called 180 ATC.

Officers noted that the spike in female involvement has been a trend for at least two years, though the number of female shooting victims is down 22 percent from last year—consistent with figures for both genders across the board. Still, they say they plan to pay particularly close attention to the uptick in violence involving female victims and suspects.

The city's 301st murder this year also occurred over the weekend. Commissioner Kelly was eager to offer some context: There are 36 more days before the start of the new year, he said, and the city currently has 8.4 million inhabitants. In 1990, the city had a population of 7.3 million, and saw 2,245 murders. But why? Kelly was hoping you'd ask.

"What we say, and what we believe is the answer, is proactive policing targeting high crime neighborhoods," he said, adding that 2,657 guns have been plucked from the street this year alone, and that shootings and homicides citywide are down 21 percent on top of 2012’s record low. "It has kept guns out of dangerous hands, and it has prevented New Yorkers from becoming victims on a significant scale."