The deceased persons have been identified as Usha and her relative Aniket (25), while Usha's son Rajiv (26) is reported to be critical, said police.
According to the police, the incident was reported around 1.30 pm yesterday when the trio, all sanitation workers, were approaching from Jharoda village. As they reached a sharp turn, Rajiv lost control and hit the school bus.
After the incident, the bus driver was so scared that he abandoned the vehicle and fled. The school children later had to be shifted to another bus. Meanwhile, the trio was rushed to AIIMS Trauma Centre, where Usha and Aniket succumbed to their injuries.
A police team is searching for the driver who is absconding, police added.