When God created Adam and Eve, they were perfect. God declared that their creation was “very good”. (Genesis 1:27, 31.) They were placed in the Garden of Eden where the living conditions were perfect and everything necessary to sustain their lives was provided. God had warned Adam not to eat from the Tree of Knowledge of Good and Evil and that eating from the tree would result in his death. Genesis 2:16-17 (CSB), “And the LORD God commanded the man, ‘You are free to eat from any tree of the garden, but you must not eat from the tree of the knowledge of good and evil, for on the day you eat from it, you will certainly die.’”
Adam disobeyed God’s command and sinned. By sinning, he forfeited his right to everlasting life. Since that time all of Adam’s children (us) have been born under that same death penalty. We inherit the sins (or imperfections) of Adam. Therefore, because Adam lost perfection, he could not produce perfect, healthy offspring. The most he could do was spawn a sinful, dying human race. “Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men,” Romans 5:12.
So, in essence, it was Adam who was the killer of God’s creation, though Satan had a hand in it by lying and deceiving Eve. But God, foreknowing that this would happen, already had a plan for humanity’s redemption through Christ. 1Peter 1:19-20 (NLT), “It was the precious blood of Christ, the sinless, spotless Lamb of God. God chose him as your ransom long before the world began, but he has now revealed him to you in these last days.” 1 Corinthians 15:21-22, “For since by man came death, by man came also the resurrection of the dead. For as in Adam all die, even so in Christ shall all be made alive.”