I'm sorry for your loss. Because your father had such a major heart attack
, he was at risk for this to happen. That is why he was kept in the hospital for days---to monitor his condition. It may have been that he developed a sudden and lethal heart rhythm disorder
, or the part of the heart that was damaged with the heart attack may have ruptured. These are the most common scenarios when this occurs in this time frame after a heart attack. Someday we'll be able to prevent this stuff, but it still happens.