The crime was captured on camera.
On the video, another man is seen entering the restaurant, briefly then walks back out onto the street. Suddenly, he lunges across the sidewalk and opens fire, blasting Winn with at least three shots to the abdomen and chest.
Stunned onlookers called the police, who arrived on the scene moments later followed by EMS medics, but Winn would be dead in a matter of minutes.
Tracey Winn, his mother from Rock Hill, South Carolina, says her son was visiting relatives in Brooklyn at the time of the shooting.
It happened at 7:45 on Saturday night, less than a week after another young man was murdered in an apartment complex in Brownsville. That is another shooting that remains unsolved.
Relatives say Trevonne Winn's murder makes absolutely no sense. That he had very few friends here and no known enemies, either.