This just isn't true. They felt exactly the same as OP up until the moment they died. A sudden death is, by definition, something that can not be regretted.
I'm sure you are not surprised to hear that many disagree with this.
As for what happens in the realm of death, we'll see when we get there.
I wasn't clear enough. The decisions one makes during their life are affected by whether or not they care about anything that happens after they are dead (any many specifics beyond that). Many people do things whose primary impact won't be felt until long after they are gone. So it isn't true to simply say that nothing matters after the individual is dead.