"The deceased, identified as Rajan Chand was flying kite from his roof on Friday when he snapped another boy's kite.
"The other boy got angry and told him that he would have to face dire consequences, but Chand thought of it to be a passing remark," said a police official.
On Saturday at around 7 PM, Rajan and one of his friend were attacked by a group of four boys including the youth who had threatened him.
They were rushed to Guru Teg Bahadur hospital where Rajan was declared dead and his friend is undergoing treatment.
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A case of murder has been registered at the Harsh Vihar police station and a manhunt has been launched to apprehend the four boys.
Two more murders were reported in the national capital in the last 24 hours, police said.
The second such incident took place in Chandni Mahal area of Central Delhi where one Shahzada Fazil alias Lucknawa (28) was shot at by two biker-borne men on Saturday evening.
The deceased had cases of attempt to murder, extortion and arms act against him.
In another such killing, which took place in Alipur area in Outer Delhi, a 30-year-old man who worked with a multi-level marketing company in Subhash Palace was murdered at his rented accommodation in Old Alipur area in the wee hours on Sunday.
"The deceased has been identified as Bharat Lal. His throat was found slit by unknown assailants. After the attack, Lal tried crawl to the neighbour's door to ask for help but fell unconscious," said a police official.