Well, this has been happening for ages. Each summer, kids have been falling over dead while playing sports, in particular basketball, football and baseball. Basketball, being a year round sport for the past several seasons, claims a lot of young kids, mostly junior high age.
Football practice begins in late July or early August and that sport will also claim several student's lives and baseball, which we think of as a sport which should not be all that risky, takes it share of lives, as well. In summer when the heat is at its' worse, we can become easily dehydrated. This is serious enough, but when you put a kid out on the field for football practice in 85 or 90 degree weather and if that kid already has an unknown heart defect, add to that dehydration, his chances of not becoming ill are slim.
The main reason for death among these youngsters is normally heart related. High school and college athletes are mandated to get a physical before beginning practice, but doctors cannot see inside the heart to know if it is really healthy or not. I have known a few kids myself that have died suddenly. It's really devastating for the parents.
I also remember a kid, maybe 12-15, that was a catcher on a baseball team down in Texas, I believe, and he was hit in the middle of his chest with a foul ball and it stopped his heart. A heart can be stopped (or started) by a sudden and sharp hit to the chest.
Back in the day, football coaches were not allowing their kids enough rest time between doing practice drills and also to become re-hydrated. A lot more kids were falling over, either dead or passed out due to being severely dehydrated. Today, the NCAA (college) and the NFHS (high school) have put forth rules that coaches should follow to make sure that the kids are getting enough time between drills and also to stay hydrated.
Hot days, none to very little rest and lack of fluid all add up to the perfect storm for having a sunstroke. Water has since been replaced by Gatorade. I have done my own research on Gatorade and have found it to be very good, "IF" you are drinking it while training. It is high in sugar and unless you burn it off, we all know that sugar will eventually turn into fat. Personally, I would also stay away from Gatorade's newest version named G2.