Leandre Mallinckrodt, of Monroe, New York, was stabbed in the neck Monday evening along the main parade route at Bedford Avenue and Eastern Parkway, police said.
He was taken to Kings County Hospital where he died, cops said.
Mallinckrodt was the first victim in a slew of violent attacks that erupted shortly after the festive parade, which annually boasts more than 3 million parade-goers.
Nifredo Veras, 26, was fatally stabbed in the neck a half hour later at a Chinese restaurant about 10 blocks away.
Police arrested Gabriel Hernandez, 21, in that attack. He was subsequently charged with murder and criminal possession of a weapon.
And about 6:30 p.m., a man and a woman were shot in the hip in front of 650 Eastern Parkway, between New York and Brooklyn avenues.
No one has been arrested in the shooting.
In Mallinckrodt's killing, cops are encouraging people to come forward with information.
The four suspects are young men between the ages of 20 to 25. The men are described as having thin builds.
Anyone with information in regard to this incident is asked to call Crime Stoppers at 1-800-577-TIPS (8477). The public can also submit their tips by logging onto the Crime Stoppers website at WWW.NYPDCRIMESTOPPERS.COM or by texting their tips to 274637 (CRIMES) then enter TIP577.