Dodi Soza, 16, was a junior running back at Downey High School. The 16-year-old had been listed in critical condition after collapsing.
After first being taken to nearby St. Francis Medical Center, Soza was transferred to Miller Children's Hospital in Long Beach where he died.
Clutching white balloons and candles, students, staff, parents and Downey High School football players gathered Saturday night at the school in memory of Soza.
The emotional vigil brought out hundreds of people. Many were stunned by the popular player's death.
"I just know that he was a really nice guy. He was a really strong guy, and everybody really thought he was going make it," said Molly Donahue, a student at Downey High School.
Witnesses say moments after scoring a touchdown, Soza collapsed on the field.
Albert Garcia, a registered nurse who was at the game watching his own son play, ran to the field and treated the teenager until paramedics arrived.
"I ran out there, and I noticed that he was on the ground, unresponsive," said Garcia. "I immediately went into CPR mode and began compressions and did what I could to try and save him."
Students say the show of support at the gathering helps ease the pain of losing a classmate.
"Not only was it Downey High School, it was the whole community," said George Estephan, a student at Downey High School. "Warren High School, our rivals, they still showed up and put balloons all over the school. It was honestly a blessing to see everyone come together."
The vigil ended with a spontaneous tribute.
It's unclear if playing football was the cause of Soza's death. An autopsy will be conducted to determine how the teenager died.