Authorities said the woman, 50-year-old Chandrika De Silva, was standing outside of her parked vehicle after putting her 5-year-old grandson into a car seat.
That's when a Jeep Cherokee driven by an allegedly intoxicated driver crashed into De Silva and two parked cars, including the Toyota Prius containing the toddler.
Richard Buitron, 22, a Marine from Fresno, was behind the wheel of the Cherokee.
The boy was ejected from the car into the street. Unconscious, he was airlifted Children's Hospital. He regained consciousness after boarding the helicopter and was in stable condition as of 4 a.m. He was admitted to the hospital's intensive care unit but is expected to recover, Los Angeles Police Department officials and family members said.
De Silva died at the scene after being pinned and crushed under the impacted vehicles.
Standing at the spot where De Silva was last seen alive, family and friends gathered to pray Sunday night.
"Every morning, kiss your mother, kiss your daughter, kiss your son, give them a hug, let them know you love them because you never know what's going to happen," said De Silva's son, Chatura.
Police said De Silva, her husband and their grandson had just returned from a party in Cerritos.
Their Prius was halfway in their driveway as De Silva's husband went to go unlock the gate.
Her grandson was critically injured, but family members said the car seat saved his life. "I think she was the angel. She loves him and I know she saved him."
"I think my mom took the step to save my son," said Aruni Ganewatte.
Buitron suffered minor injuries. He was taken into custody.
On Sunday night, members of the Sri Lankan community gathered to mourn their loss.
The De Silva family immigrated to the United States in1990 after winning a green card lottery in their native country.
Ganewatte said her parents lived the American dream working at a fast food restaurant and cleaning homes to put their three kids through college.
Now she said her family's loss in unimaginable.
"What was he thinking?" Ganewatte said. "And he was a Marine? And he's supposed to serve the country and take care of people?" Neighbors said they heard the crash and immediately rushed out to help.
"I heard a bunch of yelling and screaming," said Kevin, a neighbor. "I thought it was a fight, but by the time I got out here I saw a car that was flipped over. I tried helping, I tried giving a hand, but by that point there was really nothing I could do about it."
"There are several factors," Officer Melisa Lisenby said. "We're still investigating if it is speed. We're not certain yet. We still have to finish our investigation but it is a possibility that it could be speed, and DUI is also being investigated at this time."
"She was a friend of mine," said neighbor Margaret Karunarotne. "She was a very good person out to help people."