A gunman walked up to the victim as he stood in a crowd of people at the memorial outside George Walker Jr. Park, at around 10:30 p.m. Monday.
The gunman fired once and fled.
The male victim felt pain in his left shoulder and was transported by ambulance to Brookdale Hospital, where he was listed in stable condition with a gunshot wound.
No arrests were immediately made.
The memorial was being held after a drive-by shooting at the park on Vermont Street Sunday left two teenagers dead and another wounded.
Police released surveillance video of the late model Honda CRV sought in that case.
A 16-year-old was shot in the head and pronounced dead at the scene. He was later identified as Kleimer Mendez of Brooklyn.
An 18-year-old was also shot in the head and taken to Kings County Hospital where he died on Monday. He was identified as Antonio Villa of Queens.
The third victim, a 17-year-old, suffered a gunshot wound in the leg and went to Brookdale Hospital in stable condition.
NYPD Commissioner Dermot Shea said the criminal justice system is not working.
"It's going to take all different parts," he said. "It's going to take prosecutors, courts, people participating in the system coming forward as witnesses. When you receive that summons to take part in the grand jury process. We have to get our hands around what is going on right now."
Mayor Bill de Blasio said the city is facing a "perfect storm."
"We know there has been an uptick in shootings in recent weeks, we know there has been a real problem with violence that must be addressed," he said. "The best way to address it is with communities. You see all over the city, community members stepping forward, elected officials, clergy, Cure
Violence movement and crisis management system, a whole host of people and organizations occupying the corners, taking back the neighborhood, making clear that violence will not be acceptable."
The mayor reiterated that the city's court system must fully reopen.
"There's a huge backlog when it comes to cases involving violent crime," he said. "Only 50% of firearms charges have even gotten to the (stage) of indictment."
De Blasio said he sent a letter to the five district attorneys, and the chief judge vowing to help in any way he can
"I've sent this letter, this morning, to the chief judge, the five district attorneys, saying let's all work together let's get this right," he said. "What can the city of New York do to help each of you and all of your colleagues to get this right?"
RELATED: 2 fatally shot in same Brooklyn neighborhood just hours apart
* More Brooklyn news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube