Cecilia Villanueva sat helplessly in the backseat and watched her 10-year-old daughter turn blue as her husband raced them to the hospital in a panic.
Earlier, the fifth-grader, Joanna Ramos, had come home from school vomiting and complaining of a headache after a fight with another girl.
Before she passed out on the family couch, she told her mother an 11-year-old girl had punched her in the head.
"I could see her lips turning purple, and I got so scared. I tried to do CPR," her mother said Tuesday, choking back tears. "I tried my best, but when we got to the hospital they said her heart was stopped. They tried, they tried so hard."
Joanna was pronounced dead Friday night after emergency surgery for a blood clot on her brain, her 17-year-old sister, Vanessa Urbina, said.
The Los Angeles County Coroner's Office labeled the case a homicide and said Joanna died of blunt force trauma to the head. Police said they have made no arrests and were conducting an investigation that will be presented to prosecutors when it's completed.
The girl's family and friends are stunned and struggling to understand how a schoolyard fight over a boy could end in death for a bubbly girl who loved to dance and sing and had a penchant for curling her long, dark hair. Joanna would have turned 11 on March 12.
Police, who are still investigating, have said the fight in an alley after school Friday lasted less than a minute, involved no weapons, and no one fell to the ground.
While the circumstances of Joanna's death are tragic and extremely unusual, medical experts said a blow in just the right spot can often prove fatal.
"This is rare, in that I've never seen it in a female, certainly not in a female adolescent," said Dr. Keith Black, a neurosurgeon at Cedars-Sinai Medical Center.
Fights involving young children, including girls, are increasing nationally, in part because of the wired world children now live in, said Travis Brown, a national expert on bullying and school violence.