When God created us with the capacity to choose between good and evil, we choose evil. Adam, the first man, chose to disobey God. All of us have ratified that choice. When Adam sinned, he caused the entire world to come under the effects of sin. We live in an imperfect world, everywhere infected by wrong attitudes, and wrong deeds.
Evil is in the world.
And none of us are exempt from it. Bad things happen because bad people do bad things. There is also a powerful evil force in the universe. He name is Satan. He is also a creation of God.