The 15-year-old boy later surrendered before the police saying that he had stabbed a man who was beating him, they said.
The incident last evening was triggered by an argument that arose between the minor and one Dipak, a resident of Raghuveer Nagar, while they were consuming liquor in the area.
Police said the duo after drinking beer started fighting and Dipak allegedly thrashed the minor after the dispute. He also chased the boy to his house in Block IV in Kalyanpuri where he again beat him up.
In a fit of anger, the minor stabbed him thrice, on the chest, stomach and waist, killing Dipak on the spot, the officer said.
Both the minor and Dipak had past criminal history. Dipak had 4-5 criminal cases registered against him and had been in jail, he said.
The minor has been sent to a juvenile home after he surrendered at the police station. A case under relevant sections of the law has been registered and he will be produced before a magistrate, the officer added.