Four persons, the shopkeeper Lekhchand, his sons Gaurav, and Vicky and their friend Dipak have been arrested.
The victim, a class 9 student, had gone to buy asafoetida from a local grocery store in Molarband area on November 23.
But he had some argument over its price as Lekhchand allegedly charged him Rs 5 more, said a police officer.
Later, the matter was sorted out by victim's father but he went missing while going to school on November 28.
According to police, Gaurav and Vicky wanted a revenge and teach a lesson to the victim for arguing with their father.
Gaurav met the boy and managed to take him to a place in Faridabad where Vicky and Dipak were waiting. The trio allegedly thrashed him badly and when he fell unconscious they admitted him in a private hospital in Okhla and ran away, where he died during treatment, added the officer.