The accident took place on the night of May 19 when both victims along with two other friends got out of their car to help people injured in another accident on the Rama IX Bridge.
The 18-year-old driver had not contacted police till a summons was issued to his paternal grandmother, 81-year-old Hong Sae Lee, who is the owner of a Mini Cooper he was allegedly driving at the time of the accident."
Recordings from security cameras revealed the licence plate number of the car that hit the victims," police said.
Hong showed up at the Thang Duan 1 Police Station Tuesday with her grandson and his lawyer, Kerdphon Kaewkerd.
The Nation