Why is a distressing spirit said to be from God?

1 Samuel 16 reads: > 14 But the Spirit of the Lord departed from Saul, and a distressing > spirit from the Lord troubled him. 15 And Saul’s servants said to him, > “Surely, a distressing spirit from God is troubling you. 16 Let our > master now command your servants, who are before you, to seek out a > man who is a skillful player on the harp. And it shall be that he will > play it with his hand when the distressing spirit from God is upon > you, and you shall be well.” and: > 23 And so it was, whenever the spirit from God was upon Saul, that > David would take a harp and play it with his hand. Then Saul would > become refreshed and well, and the distressing spirit would depart > from him. Why is the distressing spirit said to be from God, as God is good? EDIT: This C.SE question addresses the question "How can a Wholly Good God Deliberately Create Evil?" In this question I am looking for the reason why the distressing spirit is addressed to God, and not, for example, to satan.