Dad finds children, mother-in-law killed in crash after they called for help with vehicle

(INSIDE EDITION) - A husband arrived to find his two children and mother-in-law dead after his wife called him to tell him their car had overheated.

A woman, her two children and her mother had pulled over on a California freeway when the engine of their Honda overheated.

Maria Briseno, and her mother, 58-year-old Maria Rodriguez, stepped out of the car and were standing with the good Samaritan who had pulled over to help when a suspected drunk driver in a white Nissan slammed into their car.

The impact killed the two 12-year-old children in the backseat, Isaac Briseno and Ailyn Miguel¸ and Rodriguez.

Briseno survived the crash and was transported to the hospital.

"You can't put into words. She's not stable," relative Rocio Ramirez told ABCNews."It's something that I think is going to take a long time for her to cope with it. It's tough, she lost both of her kids and her mom."

The good Samaritan, 60-year-old Jose Prieto, was also killed, reports said. Prieto's family said it was very much like him to offer help.

"That's just like him. He sees a car pulled over, dead in the street, he goes and he helps," Prieto's daughter, Monica, told CBSLA.

The suspected drunk driver, Luis Sanchez, 64, was transported to the hospital.

He was being held pending toxicology tests.

Authorities said Sanchez refused to speak with them.