The violent crash occurred in the 900 block of South El Camino Real shortly before 1:30 a.m.
Investigators say the car, a late-model BMW, was headed south when it struck a lamp post and a palm tree. The car was split in two.
"It was quite a horrific scene. It appears that some of the occupants were actually ejected from the vehicle," said Lt. Jeff Hallock of the Orange County Sheriff's Department. "At this point it's very preliminary in the investigation, but it appears that both speed and alcohol are factors in the collision."
The only survivor of the crash, identified as 24-year-old Josephine Garcia, was airlifted to a local trauma center for treatment. She is expected to survive.
The deceased victims were identified as 25-year-old Pablo Vargas Diaz of San Juan Capistrano, 26-year-old Martin Junior Nieto of Laguna Niguel, 27-year-old Lucia Garcia Solis of San Juan Capistrano and Louis Silva.
A makeshift memorial was growing at the scene of the car crash Saturday night.
"We grew up together, we went to elementary school together, and we've been friends since," said Diana Sanchez, a friend of the victims. "It's a small town, so we all know each other. We stayed close."
Relatives of the victims consoled each other while visiting the accident scene and memorial. Friends say Pablo Vargas was driving the car.
"It's just tragic, it just really hurts," said Juan Anguiano, a friend of the victims. "Especially Pablo, he was like a brother to me. He was always looking out for me."
"I feel the loss for every single one of the families that lost their son, daughter. It's very unfortunate this happened," said Anna Florentino, a relative.
The crash is the first quadruple fatal accident since the sheriff's department began policing the area in the 1960s.
Investigators are still looking into the crash. If you have any information about this incident, you're urged to contact the Orange County Sheriff's Department at (714) 647-7000 or (949) 770-6011.