One woman has died after Thursday night's hit-and-run crash atop Twin Peaks and now her son, who witnessed the incident, is left to mourn her loss.

Police responded to the crash Thurdsay night on Christmas Tree Point Road. Three pedestrians were struck by a gray sedan and knocked from the road onto the hillside, police said.

Kai Yuan's mother, Yuee Yao, was one of the victims and she was pronounced dead at San Francisco General Hospital Thursday night. Yuan's best friend and the friend's wife, who were also struck, were still in the hospital Friday recovering from their injuries.

Police said the driver of the car that hit them was drunk.

The family of 56-year-old Yao is still in shock.

Yao's only son, Kai Yuan, told KTVU he had taken her and his two friends who were visiting from Wisconsin to Twin Peaks around 9 p.m. Thursday to see the beautiful view.

He said they were walking down the road when a car sped toward them.

"I saw suddenly a pair of engine headlights in front of me and then as instinct I just jumped over the wall," he said. "After I stood up, I can't find my mom. She's gone."

When he stood up, he saw that his mother and friends had plummeted about 30 feet down the steep hillside.

"I called their names," he said. "I heard my friend's voice. His wife's voice, but not my mom's. No response. There was no response."

His friends were badly injured, and when he found his mother he said he knew when he saw her no one could save her.

"I held her in my arms and I just called for help," he said.

Police found the suspect's car nearby in the Twin Peaks lookout parking lot and arrested the 23-year-old driver.

The woman is still in jail as of Friday night and is being held on more than $600,000 bail for felony hit-and-run and felony DUI.

"They were several obvious symptomatic signs of alcohol intoxication on the part of the driver as well as on the part of the occupants," said San Francisco police Sgt. Michael Andraychak.

An additional manslaughter charge could be added, police said.

Police also arrested two male passengers ages 22 and 25 for public intoxication. A 17-year-old girl inside the car suffered minor injuries and was taken to San Francisco General Hospital.

Yuan said his mother and father had come from China when his 18-month-old son was born.

Yao came back two months ago to help with the boy, since Yuan and his wife both work at University of California San Francisco.

Yuan described his mother a strong and loving woman who was loved by many. Yuan called his father in China Friday and told him the news over the phone.

"I would do anything to get her back," Yuan said.

Yuan said some witnesses helped him, but he wasn't able to get their names. He said hopes they'll contact San Francisco police to help with the investigation.

Anyone with information about the case is asked to call police at (415) 575-4444 or to send a tip by text message to TIP411.