What Causes Fatigue & Pain In The Chest After Running?

My 16 year old son runs track at school and yesterday he seemed tired and out of breath when I picked him up. It was very warm yesterday too (86 degrees). After he came home he went straight to bed and went to sleep. Well he said he vomited a couple of times last night and had a headache through this morning. The headaches are now over and now saying he has middle mild chest pain. He says it feels the same way that it does after he runs. His resting pulse rate is 51. I was wondering should I be concerned about anything? He also just told me the way he felt after practice, it came back last night before bed.