The signs pointed to, like vomiting, aren't that out of the ordinary in "double days" anyway (though 3 times could have signalled "get some fluids in him!"

. Many football players in the heat of the summer will throw a chunder and continue playing, especially during pre-season, when they are auditioning for playing time. Eons ago when I was in high school I once excused myself from the huddle to go decorate the grass, came back two plays later and continued mauling people. I've known long distance runners who claim to have thrown one while running and not even stopped running.
It sounds like he was pushing himself harder because he had practiced poorly, pressing to try and impress the coach, and overextended himself. By the time he hit the point where emergency assistance was rendered it was too late.
It is very sad that the man has gone, pro sports needs men with his qualities, and needs them to make the headlines for their positions as role models rather than from a tragedy like this. My condolences to his family.
KF