Family members identified the toddlers as Alinah Flores, 3, and Neveah, 4.
The crash happened just after 11 p.m. at Walnut and Riverside avenues, according to Sgt. Daniel Smith with the Rialto Police Department.
"It's a tragedy. Two innocent babies got their lives taken away," said the girls' grandmother, Lisa Taylor.
Family members gathered at the scene of the crash for a somber vigil to mourn the heartbreaking loss of the two little girls. Flowers, candles, stuffed animals and balloons were placed along the curb.
"They were a joy. We would have tea parties, riding bikes, I'm at a loss for words," said Taylor.
Police said the girls were riding in a white Honda Accord with their parents.
The driver of the Accord made a left turn onto Walnut when the suspect, who was driving a Dodge Ram pickup truck heading south on Riverside, ran a red light and T-boned the Accord, police said. The impact of the collision sent the car careening into a tow truck, Smith said.
The two girls died at the scene. Police said they were both in car seats but one of them was ejected from the vehicle.
Their parents, 25-year-old Marky Flores and 24-year-old Valencia Avilez, were also in the car. Flores suffered moderate injuries but is expected to survive. Avilez was not injured.
Police said the suspect, identified as 28-year-old Alexis Garcia of San Bernardino, fled the scene but was later found. He had a passenger in his truck but that person was not injured or taken into custody.
Garcia was arrested on two counts of murder, one count of DUI and one count of felony hit-and-run. Police said he was being treated at a local trauma center. Once released, he will be booked into West Valley Detention Center, authorities said.
The incident remains under investigation.
"I'm angry. I have no words. We all just want justice. It's not going to bring our babies back," Taylor said.
A GoFundMe campaign has been established to help the girls' parents with medical and funeral expenses.