If someone suffers cardiac arrest or a heart attack, would they be able to call 911?

Hi all - my father unexpectedly passed away at age 60 3 months ago. He was 5’6” and weighed 220 lbs. He had a “mild” heart attack about 9 years ago and had a stint. he was prescribed the below medications by his cardiologist and PCP at the time of his death:

Atorvastatin (Lipitor) - 80 mg,

Ezetimibe (Zetia) 10 mg,

Amlodipine (Norvasc) 5 mg,

Olmesartan (Benicar) 40 mg,

Metoprolol tartrate (Lopressor) 50 mg,

Nitroglycerin (Nitrostat) 0.4 mg SL

I was going to visit him for father’s day and he was found facedown dead, with his phone right next to him. He likely passed away 4 days before he was found based on the story i pieced together. The coroner said it was likely a heart attack and did not do an autopsy.

He had been drinking more recently and I have so many questions i’m not sure i’ll ever get answers to. I am wondering based on this information, if people having a heart attack are able to dial 911. what if someone poisoned him? what are the odds that he suffered? What do these medications tell you about someone’s health?