Gee the soccer ball probably hit him in the chest at JUST the right time, in the microseconds between beats, and his heart just stopped!
When that happens (Mostly to kids) the heart is fine, just had electric signal interrupted. They took a defillibrator on the field and it didn't work. It's usually an easy fix in that situation which is why defillibrators have been common on athleltic fields for years, now, before Covid.