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Health officials and police in Long Beach, Calif., are trying to determine how an 11-year-old girl died after getting into a fight with another girl over a boy.

Joanna Ramos, a fifth grader at Willard Elementary School, died Friday night in the hospital after complaining of a headache.

"She was so nice to me; she was like a sister to me," said classmate Stephanie Soltero, crying. "They were fighting over a boy, just for a boy. It's just stupid."

The two girls and seven onlookers went to an alley off campus after school on Friday, where they had planned to fight, according to Deputy Chief Robert Luna of the Long Beach Police Department. No weapons were used and no one was knocked to the ground.

Police are waiting for autopsy results to determine Ramos' cause of death.

Ramos' classmate said she was complaining about a pain in her head during an after-school program.

"She was crying and saying her head was hurting. She said to the supervisor, the principal on call, she told them that my head was hurting and then she called the parents and the parents took her to the hospital," classmate Justin Robert King Jr. said.

Ramos was unconscious and not breathing when family members took her to the hospital at about 5:50 p.m., according to police. She was rushed into surgery but pronounced dead three hours later.

"There are times when words do not convey a sense of sadness and loss that we feel. This was one of those times. Our hearts go out to the families affected by this tragic event yesterday. It resulted in the death of an 11-year-old girl from Long Beach. It's hard to understand how this can happen. If you're like me, you're also thinking of your own children, perhaps your daughter or your granddaughter, and you get a sense of how precious life really is," Long Beach Mayor Bob Foster said Saturday.

Outside Willard Elementary School, friends left balloons, candles, stuffed animals, flowers and letters to Ramos.

ABC News affiliate KABC contributed to this report.