The Hebrew expression given in the KJV as "from the LORD" is מֵאֵ֥ת יְהוָֽה. It occurs 36 times in the Hebrew Text (WLC) of the Old Testament. For example:
Genesis 19:24 - brimstone and fire "from the LORD" rained on Sodom and Gomorrah
Numbers 11:31 - quail "from the LORD" fell over the camp of Israel in the wilderness
Numbers 16:35 - fire "from the LORD" consumed Korah and all the others who joined him in the rebellion against Moses.
Joshua 11:20 - a spirit (implied) "from the LORD" strengthened the heart of the fighting men of Israel, enabling them to route the kings of Canaan - 31 kings (1) in around 6 years. (2)
All these declarations are accompanied by miraculous events, which the authors of the text could only attribute to the LORD. However, given the existence and availability of the narratives in the canon of scripture, there is now no excuse for not seeing the bigger picture that they paint.
The record of the dialogue in chapter 1 of the book of Job is extremely important in regard to seeing the broader picture being drawn by the entire narrative of scripture.
7 And the LORD said unto Satan, Whence comest thou?
Then Satan answered the LORD, and said, From going to and fro in the earth, and from walking up and down in it.
8 And the LORD said unto Satan, Hast thou considered my servant Job, that there is none like him in the earth, a perfect and an upright man, one that feareth God, and escheweth evil?
9 Then Satan answered the LORD, and said, Doth Job fear God for nought? 10 Hast not thou made an hedge about him, and about his house, and about all that he hath on every side? thou hast blessed the work of his hands, and his substance is increased in the land. 11 But put forth thine hand now, and touch all that he hath, and he will curse thee to thy face.
12 And the LORD said unto Satan, Behold, all that he hath is in thy power; only upon himself put not forth thine hand.
So Satan went forth from the presence of the LORD.
-- Job 1:7-12 (KJV)
There is way more happening in this passage than a wager between two buddies (a la the Hollywood movie, "Trading Places"). Satan is not the LORD's buddy, but his rival.
Satan says to the LORD, "... put forth thine hand now, and touch all that he hath, and he will curse thee to thy face." Would a buddy suggest to his buddy, "The only reason for the reverence shown to you, is expectation of gain. Stop the blessing and the worship will become curing? What else is there about you that could possibly motivate his reverence?" No, such sentiments come from a heart that is, itself, proud and irreverent.
Satan says, "Hast not thou made an hedge about him, and about his house, and about all that he hath on every side? thou hast blessed the work of his hands, and his substance is increased in the land." What is this "hedge" that Satan mentions?
The "hedge" is clearly the protective hand of the LORD. Why would the existence of God's protective hand be an issue for Satan. Surely, it can only be, that it has hitherto prevented him from doing what he is compelled in his heart to do: move others to want to curse the LORD to his face.
The LORD says to Satan, "Behold, all that he hath is in thy power; only upon himself put not forth thine hand" The disasters that befall Job from this point in the narrative are the work of Satan's power, and Satan's hand. It is true that the LORD has allowed it, but the concluding chapters of the story of Job reveal the reason the LORD gave Satan the keys to the hedge, as it were.
All those who recognize the narrative of scripture to be a record put together, preserved, and published by honest hearts who are reverent towards the LORD, and that it depicts the good, the bad, and the ugly of human-to-human/human-to-God relationships, will understand that righteous souls are vulnerable to wickedness. Except for the "hedge" (the protective hand of the LORD), they would be overwhelmed by the wicked, and consumed.
What should the LORD do, if life within the hedge becomes no different to what life would be without it, i.e. those within the hedge forget that it is there and imagine the blessings they enjoy are because of their own strength and their own goodness. Well, he'd have to take it away to show them that such is not the case, wouldn't he?
That is precisely what the LORD did in Job's case, to prove to him that he could do nothing without His hand of protection, that his strength was completely inadequate for the task of keeping himself and his family safe.
6 Then answered the LORD unto Job out of the whirlwind, and said, ...
8 Wilt thou also disannul my judgment? wilt thou condemn me, that thou mayest be righteous? ...
10 Deck thyself now with majesty and excellency; and array thyself with glory and beauty. 11 Cast abroad the rage of thy wrath: and behold every one that is proud, and abase him. 12 Look on every one that is proud, and bring him low; and tread down the wicked in their place. 13 Hide them in the dust together; and bind their faces in secret. 14 Then will I also confess unto thee that thine own right hand can save thee.
-- Job 40:6, 8, 10-14 (KJV)
###Conclusion### "from the LORD" is an expression that one can excuse from those who had no access to the entire narrative of scripture, but there is no excuse for those who now do. Of course, the LORD takes full responsibility for the fact that evil exists, since if it was his will, he would have prevented it. However he is not the agent of destruction. Beings who have CHOSEN to oppose him, whose hearts are proud and defiant, and whose greatest desire is to usurp the reverence and honour that is due him, are such.
But like all who are proud and defiant and boast of their own intellect and strength, drawing attention to their own accomplishments, and building edifices to themselves, they have no concept of what architect of the universe is doing from beginning to end:
9 For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts. 10 For as the rain cometh down, and the snow from heaven, and returneth not thither, but watereth the earth, and maketh it bring forth and bud, that it may give seed to the sower, and bread to the eater: 11 So shall my word be that goeth forth out of my mouth: it shall not return unto me void, but it shall accomplish that which I please, and it shall prosper in the thing whereto I sent it.
-- Isaiah 55:9-11 (KJV)
Even when it is explained to them, they can't grasp it:
Behold, ye despisers, and wonder, and perish: for I work a work in your days, a work which ye shall in no wise believe, though a man declare it unto you.
-- Acts 13:41 (KJV)
The evil spirit "from the LORD" spoken of in 1 Samuel 16:14, is the best the author could do to explain what he observed in regard to Saul. But as explained above, it is just another example of the LORD removing the hedge (his hand of protection), from those who have forgotten that it is not their own hand that saves them, but the LORD's.
What will happen to Saul when all things are concluded? Did he repent in dust and ashes, like Job? Those are questions for another time.
Notes: (1) - Joshua 12:24 (2) - [BibleHub Time-line][1]: Joshua chapter 1 (1405 BC) through to chapter 13 (1399 BC)