Heather, 16, and her boyfriend, Nathan Koontz, 19, had been hit by a pick-up truck while crossing PCH at 6th Street.
The Huntington Beach girl had left her identification in the car, so the family asked police if one of the victims was Nathan Koontz.
"It's something you're talking yourself out of," Stacy Stamm said. "And then I saw her shoes [on the ground]."
Then they knew. Heather died.
Koontz, of Fountain Valley, was taken to UCI Medical Center in Orange where he was treated for multiple injuries.
A man who identified himself as Nathan Koontz's father said Tuesday his son was conscious but suffered a head injury.
Jerry Koontz waited with his son in intensive care Tuesday afternoon at the UCI Medical Center before Nathan went in for surgery.
He's got a broken arm, a large gash on the head, both ankles are sprained, "but nothing too serious, thank God," Jerry Koontz said.
Jerry Koontz was more worried how his son would cope with Heather's death.
"He loved her," Jerry Koontz said. "That was the love of his life. They were best friends, completed each other's sentences. They matched."
Unable to express how sorry he was for Heather's family, Koontz cried for the girl who meant so much to his son.
Heather Stamm had one of those smiles that made memories for her friends and loved ones.
Greg Goran, her world history class teacher last year, said it would even pop up at the oddest moments.
"She always did it with a smile, even when I busted her for something she shouldn't be doing," Goran recalled Tuesday as he tried to make sense of Monday's accident.Goran sat with Heather's close friend, Lauren Phillips, after school Tuesday to reminisce about her.
Before class Tuesday morning at Huntington Beach High School, Goran was handed a memo telling him about Heather's death.