The Bible tells us that mankind is inherently evil. They are, and I attribute their evil to the same source as the Devil's. It wasn't God for he is inherently good-- at least it wasn't him, directly. God is the ultimate free moral agent: he is sentient with powers of will and choice. That he made mankind and angels with similar powers and turned them loose in creation with freedom-- that is the root of evil.
How can those abilities which so distinguish us from the plethora of slime and the menagerie of the mobile be responsible for evil? Let me define evil before proceeding: evil is that which is not good, and by extension, that which is out of harmony with God. Evil is un-God. When choice and will were expressed independently of, and in opposition to God, evil was born.
Evil was the the risk intrinsic in freedom.
All that is was made, was made as home to mankind, God's crowning creation. When man embraced evil and shattered the crystal of that pristine environment, they alienated both the creation and the creature from God and what is good. As a result, sin and death and evil are the fruit, and have spattered everything in the universe with their rot, including all that is alive and inanimate. Man, beast and the environment we live in has all been tainted by evil.
All that is was made, was made as home to mankind, God's crowning creation. When man embraced evil and shattered the crystal of that pristine environment, they alienated both the creation and the creature from God and what is good. As a result, sin and death and evil are the fruit, and have spattered everything in the universe with their rot, including all that is alive and inanimate. Man, beast and the environment we live in has all been tainted by evil.
Creation still bears the fingerprints of God, but its smudges betray, all too clearly the cost of image bearers going their own way.