Officials identified the three family members and a good Samaritan who were on the side of the 10 Freeway in Fontana with a broken-down car when they were killed on Friday.
Two of the deceased were step-siblings Ailyan Miguel and Isaac Briseño, both 12, according to the California Highway Patrol. Their grandmother, 58-year-old Maria Luisa Rodriguez, was standing outside the family's overheated Honda with the children at the time of the crash and was also killed.
The children's mother, Maria Briseño, 39, was not harmed in the crash, though she was transported to Arrowhead Regional Medical Center because of her hysterical state that paramedics feared could turn into a heart attack.
All four were residents of La Puente. They had been driving to San Bernardino to spend part of the weekend with relatives, family members said.
A man who had stopped to help the family was also killed. His daughters identified him as Jose Prieto, 60.
“He was a person that loved God very much," Monica Prieto said of her father. "He was always there to help somebody in need.”
A second daughter, Esperanza Garcia, echoed the sentiment, saying he "never thought about himself."
Officials said they were issuing a warrant to conduct a blood test on Riverside resident Luis Sanchez, 64, who they suspect could have been driving under the influence when his Nissan Frontier slammed into the rear of the Briseños' Honda around 12:35 p.m.
Sanchez told CHP officials he was on the way home from work and fell asleep, but footage from the scene showed a beer can wedged beneath the driver's seat of his truck.
He was transported to Arrowhead Regional Medical Center to be treated for minor face and neck injuries, authorities said.
The Briseño family pulled their car over to the side of the eastbound 10 near Cherry Avenue after it became overheated. Spotting their trouble, a man driving a Toyota Tacoma also pulled over the help them out, stopping his truck in front of the sedan, according to the CHP.
The three adults were standing outside the vehicles when Sanchez's Nissan slammed into the Honda, which the two children were inside of. The Honda was then pushed forward into the Tacoma.
Rodriguez, the two children and the Toyota driver were all pronounced dead at the scene.
Prior to the deadly crash, Briseño had called her husband and son to let them know that her car had broken down on the freeway; when they arrived, they found three of the four family members dead, CHP officials said.
Prieto's family has also set up a GoFundMe page to help cover funeral expenses. In total, the various pages have raised over $35,000 so far.
The family of the grandmother and two children killed also held a fundraiser at a family member's home in Bloomington on Saturday.
"Just thinking about the kids ... I don't think there's even words to explain how tough that would be on the parents," Rocio Ramirez, an aunt of the two children, said.
Authorities are pushing forward with their investigation into whether alcohol played a role in the crash.