A 37-year-old man was stabbed to death during an argument apparently over one man not saying ‘thank you’ to another at a smoke shop in United State’s Brooklyn, reported CBS News.

The fatal argument was caught on video inside and outside the shop on 4th Avenue in Park Slope.

The footage shows the beginning of the confrontation between a man in a white t-shirt, who wound up stabbed to death, and a man wearing a backpack, possibly for a job delivering food.

Eyewitness and employee Kharef Alsaidi told CBS, “It was just about not saying ‘thank you’ for opening the door for him.” Sharing more details, Mr Alsaidi said, “Why don’t you say, ‘Thank you for opening the door’?” To which the suspect responded, “I didn’t tell you to open the door for me.”

After a few moments of confrontation, things got physical and violent, and moved outside the store. The victim also dared the suspect to stab him. Moments later, the suspect grabbed a knife from his bicycle and stabbed the victim in the abdomen and neck.

Alsaidi said, “The victim started screaming, ‘He stabbed me, he stabbed me,” and then he stumbled back into the store and was bleeding all over the floor.

The victim was taken to New York Presbyterian Brooklyn Methodist Hospital, where he was declared dead. No arrests have been made so far.

Alsaidi said he tried to de-escalate the problem by telling the guy, ‘Just put the knife away’.

“I did my best to de-escalate, but nothing worked,” he said.