The Lord is love itself, and that love is the ultimate source of all energy and thus of all life. It follows, then, that the more we turn ourselves toward the Lord and accept His love, the more alive we are -- and the more we turn away, the more dead we are. This is not, of course, obvious in our external, physical lives, but this life is just a shadow compared to real, eternal, spiritual life. To "kill" in the Bible, then, means to destroy someone spiritually, to annihilate the desires for good and understanding of truth that lead people toward the Lord.