Police say the bicyclist rode up to the 53-year-old victim who was also on a bike and stabbed the victim in the back, causing him to fall to the ground.
It happened Sunday around 4 p.m. on Fulton Street in Cypress Hills.
Investigators say the suspect yelled "what happened" to the delivery worker but the victim ignored the suspect.
That is when the suspect rode up to the victim and pulled out a knife before stabbing him, police say.
The victim is Asian, but the incident is not immediately being treated as a bias crime.
He suffered a non-life-threatening stab wound to his lower left back and was taken to Jamaica Hospital Medical Center in stable condition.
The attacker is described as a male approximately 5'8" tall, 160 pounds, with a slim build, wearing a green ski mask, a green hooded shirt, black pants, and black sneakers.
Anyone with information regarding this incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
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