What is truly twisted is presuming that we not only can predict someone's future, not only decide that we may act to their detriment based on this prediction, but also to kill them if based on this prediction we deem them unfit to live.
A swift painless death is at my sole discretion to prescribe to myself. I alone will decide whether my suffering is so bad as to merit death. That has no place in the hands of anyone else, not even my parents. This notion is so horrible that it's difficult to type about it without using all caps.
Whose life is it, and therefore who has the right to end it?