The incident was reported to the Police Control Room around 11 pm on Thursday
A man was stabbed to death in Aman Vihar area in outer Delhi when he tried to intervene in an argument between two men, a police official said.
The incident was reported to the Police Control Room around 11 pm on Thursday from Ugna Chowk in Prem Nagar locality.
The deceased Nitish, 27, was a labourer, the official said.
The accused Kitab Singh, alias Kejriwal, works as a cook at a restaurant and saw the two men arguing over some issue.
Nitish's brother Aatish was involved in the argument.
Under the impression that Kitab Singh was from the opposing side and that he beat his brother, Nitish thrashed the accused, the official said.
Kitab Singh got angry by the unprovoked beating and in a fit of rage stabbed Nitish in his chest with a kitchen knife, he said.
Yogesh, a student, who tried to intervene during the argument sustained injuries in his right hand in the quarrel.
A case was registered based on the statement of Rakesh, the youngest brother of the deceased.
The accused has been arrested, the official added.