A 14-year-old athlete collapsed and died during pre-season football practice in Orange County, officials said.
Tributes to Mitchell Cook now crowd the fence at Canyon High School.
"I'm shocked. He was really young. It's sad. He had a lot of potential," said Nathan Singiri, who was in chess club with Cook.
Coaches performed CPR on the teen before paramedics rushed him to the hospital, where he was pronounced dead Wednesday evening, the Orange County Register reported.
Peers said they heard what happened through social media.
"I actually got the news from Twitter," Reagan Poltrock said. "They started a feed 'Pray for the Cook family' – everybody writing nice comments about him, his family."
Classes at Canyon High School resume Aug 21. Meantime, athletes from song, cheer and football plan to honor their fallen friend Saturday in the lower football field.
"I think it's kinda hard for the kids to process, kinda hard to believe. Somebody athletic and young – something could happen like that. Really hit close to home," parent Heather Canedy said.