The most likely civil claim would be negligence coupled with intentional infliction of emotional distress for the relatives, or the fatty if it survived. However this would get thrown out because the standard for negligence is based on the actions hypothetically taken by a "reasonably prudent person/corporation" in that specific situation; a standard which Walmart could definitely meet, because a reasonable person wouldn't expect a customer to have a heartattack from walking a few feet. Also, the ham would have to prove that the heart attack had been brought on by that specific brief bout of physical exercise and not their general, degenerate condition.