I think sun stroke. Is it. how he died?

My dad felt more heat on head but his body is in normal temperature. After 3 days his body is cooled and he said a small pain in chest and felt sweat on only chest. So i immediately taken to hospital. At that time there was no doctor. So my father said take me to home . We could come at another time. I then started to take him suddenly he has fallen down and felt tough to breathe. We lift him and taken to bed. Few min after he woke up. Then i asked him what happened. He said nothing. I taught that he felt tense,so we left in hospital and started to wait for doctor. Again few minutes he got another same like before . He again woke up. I felt more tense and taught to take him another hospital. Then i cancelled op and came to my father and said him to go for another. He got it again. This time he didn't wokeup. He died. Now my question is what happened. What is it. How he died