Why Did My Father Suffer Sudden Cardiac Arrest?

My father had gone somewhere when he came back, in the evening, he had normal fever, we consulted doctor and he gave medicine, after that fever was gone for 4-5 hours but then again he got fever, this time it was 103° , we again gave him medicine to lower body temperature and consulted doctor, and got his blood test done, turned out, his tlc were 18000 and he had caught infection (God knows from where) , doctor told us to get him vaccination of monocef for 5 days (1 injection for each day) after first injection Or 2nd injection, fever was totally gone, we thought he was recovering, even he said now I have only weakness, after completing the 5 days monocef (Antibiotics) course, we again did his blood test and turned out the tlc were raised to 38000 instead of declining and his Bilirubin reached 5.9 and sgot and sgpt were raised, we took him to hospital in emergency but he was okay at that time, I mean, he sath with us in car, he said he is only feeling weakness, when we took him to emergency in the morning at 9am and from there same day they shifted him to icu at around 12 noon and the same day at night around 11-12 pm his bp dropped suddenly or idk if his heartbeat was suddenly slow, they put him on ventilator and they told us that the next 24 hours are very critical if he doesn't wake up, but next day he got conscious, he wasn't opening his eyes but he was listening, his hands were tied so he doesn't try to remove ventilator pipes and he he turning his head up and down when I was communicating with him but eyes we're closed then he again at 3 pm got an attack, sudden cardiac arrest idk how that happened again and after that he became unconscious, they revived him, hands which were tied before were opened, still I thought they will save him, his age was 65 , I thought God cannot be so cruel, I held hope but then again next day in the morning around 2:30 am he again had cardiac arrest, they again revived him and then at 5:30-6 he again had sudden cardiac arrest but this time he was gone, doctors didn't put effort like they were putting before, I told them to give him cpr again but they said they can't. Idk why, he is gone now and I am left alone, I don't understand what happened, please help me.