The victim was then stabbed in the neck and abdomen.
He fell back into the shop entrance bleeding heavily.
The victim was taken to Brooklyn Methodist Hospital where he was pronounced dead.
Speaking to ABC7, shop employee Kharef Alsaidi said: “It was just about not saying ‘thank you’ for opening the door for him.”
He said the victim asked: “Why don’t you say, Thank you for opening the door?”
The employee said he had tried to deescalate the problem and get the suspect to put the knife away but it did not work.
Police are currently searching for the suspect.