Question 134: Which is the sixth commandment?

Answer: The sixth commandment is, Thou shalt not kill.

Question 135: What are the duties required in the sixth commandment?

Answer: The duties required in the sixth commandment are, all careful studies, and lawful endeavors, to preserve the life of ourselves and others by resisting all thoughts and purposes, subduing all passions, and avoiding all occasions, temptations, and practices, which tend to the unjust taking away the life of any; by just defense thereof against violence, patient bearing of the hand of God, quietness of mind, cheerfulness of spirit; a sober use of meat, drink, physic, sleep, labor, and recreations; by charitable thoughts, love, compassion, meekness, gentleness, kindness; peaceable, mild and courteous speeches and behavior; forbearance, readiness to be reconciled, patient bearing and forgiving of injuries, and requiting good for evil; comforting and succoring the distressed, and protecting and defending the innocent.

Question 136: What are the sins forbidden in the sixth commandment?

Answer: The sins forbidden in the sixth commandment are, all taking away the life of ourselves, or of others, except in case of public justice, lawful war, or necessary defense; the neglecting or withdrawing the lawful and necessary means of preservation of life; sinful anger, hatred, envy, desire of revenge;all excessive passions, distracting cares; immoderate use of meat, drink, labor, and recreations; provoking words, oppression, quarreling, striking, wounding, and: Whatsoever else tends to the destruction of the life of any. (Here)

Why do some of us think that the death of Terri Schiavo was tantamount to murder? Because there isn't much, if any difference, between killing with intent and (intentionally) allowing someone to die by "neglect[ing] or withdrawing...necessary means of preservation of life."