My Son Passed Out Driving With Myself And His Father

My son passed out driving with myself and his father in vehicle. We managed to stop the truck without wreckibg, so no collision was involved, however after 30 seconds or so he stopped breathing. His father " beat" his chest 7 or 8 times and my son come back...slowly, sweaty, some confusion,some tingly feeling in feet. After all test available, eeg, EKG, vascular imaging, MRI, cat scan, bp, sugar, only thing cardio n neuro docs can say is low patassium ...so confused and scared. Any suggestions.my son is 23. No narcotics in system.