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"He just fell and his hands went into his body and he just started shaking, and just like had a seizure," said teammate David Sanchez.
Head coach Joe Hay says Telles had not been hit in the seconds leading up to his collapse.
The Orange County coroner's office says an autopsy conducted over the weekend is inconclusive.
There is speculation that the tragedy may be linked to an unknown heart condition, but that has not been confirmed by the coroner's office.
Teammates and the crowd watched as an emergency physician rushed from the sidelines to try to revive Telles.
Some parents question whether or not ambulance response time played a role in the football player's death.
"The ambulance wasn't there quick enough. In my opinion, it wasn't physically on the field like it should have been, but it wouldn't have made any difference," said parent Mike Smith.
"I don't know if that could have or would have made a difference," said Hay. "In talking with the doctor at the hospital, he just said it was Kevin's time."
Despite some parents saying ambulance response time to the field was slow, Alan Trudell of the Garden Grove Unified School District says the away game was staffed just like any other and that Telles received immediate treatment.
"There was an emergency medical physician who rendered immediate medical assistance at the time of the incident," said Trudell. "Cardiac defibrillation was applied as was CPR. 911 was immediately called. There was an ambulance at the field, that ambulance however was called away to render more medical assistance at that facility shortly before the incident occurred."
The Orange County Fire Authority said it arrived on scene with an ambulance within three minutes of the 911 call.
However, attempts to revive Telles failed.
The coroner's office says the official cause of death remains unknown. Officials are waiting for toxicology reports, which could take several weeks.
The head coach says that Telles was in great physical condition and he had had no problems in practice over the summer.
As the coroner's office investigates what caused the death of the 5 feet 11 inches, 200-pound senior, family and friends are remembering the good times they shared with him and the joy he brought to the lives of so many.
"He was the greatest guy you'd ever meet," said brother Robert Telles. "So many people love him. See all the stuff out here, this is all for him."
The senior football player was remembered at a memorial service Sunday night in Garden Grove. A burial has been postponed pending toxicology tests.