The locals also caught hold of the errant bus driver identified as Vikram (34) and thrashed him black and blue. He was later handed over to the police.
He will be arrested after he is discharged from the hospital following treatment.
The incident took place around 11 AM when the deceased identified as Amna Kataria was going to his school to appear for final examination.
"Clad in a school dress, he was trying to cross the road when the bus took a right turn from the red light. The driver could not probably see the boy and he came under the wheels," a senior police official said.
The locals caught Vikram and beat him up. They torched the bus and also damaged several other buses, including those parked in the nearby bus depot, the official said.
Someone made a PCR call following which the boy was taken to AIIMS where doctors declared him brought dead.
It also ordered an enquiry into the matter which will be conducted by transport minister Gopal Rai.
While addressing a press conference at Delhi Secretariat, Deputy Chief Minister Manish Sisodia said action will be taken against the driver after the detailed report.
It is a very sad incident. We couldn't compensate their loss but the government has announced to give Rs 5 lakh as financial assistance to the family, he added.
A large number of police personnel were deployed in the area to maintain law and order. As the angry mob went on a rampage in the area, traffic jams ensued in several arterial roads in south Delhi.
The police have also registered a separate case against unknown persons for rioting and damaging public property.
Some people suffered minor injuries in stone-pelting, police said.
