The accused Virendra Singh had killed his younger brother Raja on January 24, they said.
Singh and his younger brother had gone to a religious fair at Budrak village on Basant Panchami on January 24 where Singh lost Rs 500 in gambling, Maharajpur police station investigating officer R N Arjaria said.
At the fair, Raja asked Virendra to buy him a toy mobile phone to play, but the accused didn't budge.
When the two were returning home, Raja pestered Virendra to buy him the toy mobile phone and told him that he would inform family elders about his gambling loss, the officer said.
The officer said that after a thorough investigation, the police cracked the case and arrested the accused Virendra.
Virendra was produced before a court which sent him to a juvenile reform home.