They taunt and threaten to kill each other on Facebook. They brag on YouTube about beating people up and post photos of witnesses they plan to intimidate.

Members of New York City’s street crews are increasingly using social media as a way to brag about their exploits and scare rivals.

And in response, Police Commissioner Ray Kelly announced a plan Tuesday to double the size of the NYPD’s anti-gang unit.

Addressing the International Association of Chiefs of Police in San Diego, Kelly said 150 detectives will be added to the unit, increasing its strength to 300 officers, under a program he called Operation Crew Cut.

The announcement comes just two weeks after the anti-gang unit arrested 49 members of the warring East New York street crews Very Crispy Gangsters and the Rockstars. Cops were able to track them through Facebook posts bragging about crimes they allegedly committed. Kelly said sometimes gang members even posted surveillance photos of rival members they planned to target.

“For example, one gang member will post a photograph of himself in front of a rival’s apartment building,” Kelly said. “Or post surveillance photographs of rivals who they threatened to kill next.”

“Members also used social media to intimidate informants,” the city’s top cop continued. “They would post copies on Facebook of orders of protection that identified complainants. One gang leader went so far as to call another rival from prison to chastise him about one of his members snitching.”

Kelly said the unit’s new manpower will also include lawyers to help coordinate arrests and prosecution, and uniformed and plainclothes officers who address rivalries between gangs on the streets and in the subways. He cited an 18 percent decrease in murder as motivation for upping the strength of the police department’s gang division.

Small-time, neighborhood crews

The commissioner said it’s not exactly the large, established gangs like the Bloods and the Crips that are behind the social media terror.

Instead, he explained, it’s usually small groups of teens and young men who are territorial of the block they live on.

“[It’s] the looser associations of younger men who identify themselves by the block they live on, or on which side of a housing development they reside,” Kelly said.

But gang unit expansion meets criticism

Not everyone sees the unit’s expansion as the best solution for combating gang violence. Robin Holmes-Myers is the project director for a youth violence outreach program through the New York City Mission called Operation SNUG — “guns” spelled backwards.

Many of the young people she works with are affiliated with gangs or street crews. She said targeting them for arrest is only going to perpetuate a violent cycle, not rehabilitate them.

“I don’t see that as being a solution. I see that as street terrorism, in a sense,” Holmes-Myers said of Kelly’s plan. “What are you helping them do in terms of changing the mindset?”

Holmes-Myers said many teens join gangs for a sense of security and cops tend to stereotype street crew members as criminals. Operation SNUG enlists the help of rehabilitated gang members who can relate to the situations of kids in street crews and encourage them to stay in school and pursue college and a career.

“When you provide opportunities that they haven’t had because of their environment or neighborhood, then you give somebody hope that there is a way out of there,” she said.