Officers on horses and on foot patrolled Morningside Park a week after 18-year-old Tessa Majors allegedly was stabbed to death by young teenagers. Also in the park a week later is an anti-violence group called Street Corner Resources.

Iesha Sekou is the founder of the Harlem group.  She says teens don't fully understand their actions.

"Consequential thinking, the ability to think about the consequences, they don't have that,” Sekou said. “You don't have that by the time you are 14, 15, 16."

Police say the attack on Majors, who was a freshman at Barnard College, began with a robbery by three boys, 13 and 14 years old.

The NYPD admits robberies by teens have surged.

Arrests for 17-year-olds are up 10 percent, and arrests for teens 15 and under are up 25 percent, compared to last year.

Sekou thinks parents, elected officials and society must take some of the blame for misguided teens.

"I think if we are seeing a spike, then we are seeing our failure," Sekou said.

Police Commissioner Dermot Shea says the NYPD is searching for new ways to address the problem.

"We are going to be rolling out a youth strategy here and we are looking to attack this, Dean, from both sides,” said Shea. “Can we stop the robberies, can we protect victims, but can we also stop kids from engaging in this behavior? Can we pivot them off to a different way? Can we keep them out of the justice system?"

The commissioner admits youth robberies are not new, but clearly they've been increasing recently, especially in Manhattan and the Bronx.

Under the Raise the Age law, teens under eighteen can no longer be charged as adults for non-violent crimes.

"There's been some changes in the law in the last couple of years with Raise the Age. Is that having an impact? Maybe, maybe not," Shea said.

Members of Street Corner Resources say, in their dealings with teenagers, they have found out that teens definitely need more programs and activities to keep them away from violence.

Standing near their mobile command center called the Peace Beast, Sekou added, "The self confidence that usually young people develop comes from sports and sewing and dancing and singing and writing poetry and playing checkers."

Commissioner Shea says cops responsible for working in schools and with teens will need to rethink their roles.

"Can we re-imagine how we use our youth officers? There are a lot of resources already in the police department that deal with youth. We just want to make sure that we are using them in a coherent strategy," Shea said.

As police keep a watchful eye on Morningside Park, the commissioner reflects on a teen who allegedly committed more than 20 robberies.

"We had a recent case in that community, tied to a robbery pattern in that community, of a 16-year-old who had 22 arrests,” Shea said. “How does a 16-year-old wind up getting arrested 22 separate times?"

What's the right solution for a young person like that? That’s an answer he hopes police and the community can find together.