Attended a funeral a few years ago of a guy who died in a similar way. Was recovering from a badly broken leg. His doctor had told him to take it easy. He ignored those instructions and went out clearing brush on his property.
Apparently a clot went to his heart and killed him. Unfortunately his wife was out of town. By the time she got alarmed about not being able to get him on the phone and traveled back he had been dead several days. Woodland creatures had been snacking. It was a closed casket obviously.