Police used dogs to track the suspects and found blood stains a block away from the crime scene.
The victim is identified as 18-year-old Roldan Alonzo-Castro.
Witnesses were too afraid to speak on camera to Eyewitness News but they told us that the victim was speaking with a girl when he was confronted and chased by a half a dozen young men.
He was cornered on the playground, and beaten and stabbed repeatedly in the chest.
The attackers escaped and the victim later died at Kings County Hospital.
Within an hour, soccer games and pickup basketball games were going on at the park.
Other people in the area however, expressed concern for their safety.
"I don't know if that's naïve, obviously there's always an uptick in activity when it gets nice and warm out, but yeah, we walk our dog here you know, we got a baby girl, so we're here everyday all the time," said Andrew Yamato, a Flatbush resident.