It may have been the case that the pax had a pre-exisiting heart condition - but undiagnosed. This is the case for many.
It may have been the case the food did have bacteria that caused the pax to be ill.
It may have been the case that the illness did trigger a myocardial infarction (MCI) know colloquially as a heart attack.
Had the pax not had that food and the body not have been tested by the illness, they might have lived for another whole week before some other crisis triggered the MCI. Or it might not have been for a year. Which is why the Post Mortem will be crucial. If they find extensive evidence of a failing heart - then the food cannot be said to have killed him. But then, I'm not an American lawyer.
A case I encountrered last year was a many of 28. Very fit, played sport every week and had been to his gym that afternoon. No flabby belly or other obvious indicators. He dropped dead without warning and the PM found extensive heart problems that did not signal their arrival. The heart worked fine - until the last second. Some get good warning and a mild attack but many others get the big one and go straight out.
You get similar events after a mild car prang when the patient is not physically injured but the anxiety can kill them. Oh yes, that reminds of another case some 18 years ago. A man in his 30s who was not that fit but certainly OK. His mother died of a heart attack in the morning. Later that day he was rushed to hospital and died of heart failure.
Unfortunately, this is life ... and death.