Coroners say that 10-year-old Joanna Ramos died Friday night from blunt force trauma to the head, and that there was no underlying medical condition.
Grief counselors were on hand at Willard Elementary School on Monday for students trying to cope with the death.
Authorities said Ramos and an 11-year-old girl had planned to fight after school to settle a score over a boy, according to a classmate. The bare-knuckle fight was near the school in an alley, and seven others watched the tussle.
"It was dumb, I mean over a boy? There's a lot of boys out there," said Ramos' friend Heidi Gonzalez.
Several onlookers said the girls didn't use any weapons. They also said the fight lasted about a minute, and nobody was knocked to the ground.
Ramos' sister Vanessa Urbina said a family member picked her up following the fight on school grounds.
"She was throwing up in the car on her way home," said Urbina. "My mom told her to change, and she was able to change, and she was telling my mom 'I want to go to sleep, I'm tired, my head hurts.' My mom said, 'No, don't go to sleep.' My mom was looking for some paper to go to the hospital."
The victim's mother, Cecilia Villanueva, said when she asked her daughter what started the fight, Ramos simply told her the girl was her enemy, and that she didn't want to talk about it.
Later at home, Ramos was feeling worse. She laid on the sofa, and Villanueva thought she was merely resting. Then, the dog began to bark, and her mother found her unconscious.
"And her face ... like purple. I got so scared," Villanueva said.
Doctors were unable save Ramos.
Investigators say they must gather more evidence to determine if the 11-year-old girl involved in the fight should be charged with a crime. Villanueva says she is not concerned with punishment for her daughter's death.
"She's not here anymore, that's it," she said.
Funeral services for Ramos have been set for Saturday.
CORRECTION: In earlier reports we said that Joanna Ramos was 11 years old. She was 10 years old at the time of her death.