The juvenile has been detained and sent to a remand home, police said.
The incident took place on Sunday when Saabir's nephew and the juvenile had a scuffle. Saabir's family was taking the boy to his house to lodge a complaint with his parents.
But mid- way, he managed to free himself and ran away. He later returned with a wooden plank which had nails on it and, on seeing Saabir standing alone in the locality, attacked him. He also hit him with a stone and ran away, a senior police official said.
Saabir was taken by police to Guru Teg Bahadur hospital in a critical state. He succumbed to his injuries today due to the severe head injury and the excessive bleeding.
The juvenile was apprehended from the locality and was produced in front of the Juvenile Justice Board (JJB). He has been sent to 14 days custody at the observation home.