First, John 6:70 is the deciding and only scripture that needs to be the final answer to your question. TheLord Jesus Christ Himself said that one of His chosen twelve, a man, a human, was a devil.
John 6:70
Jesus answered them, Have not I chosen you twelve, and one of you is a devil?
After this scripture Jesus eluded to this fact by addressing the lineage of how a man could be a devil.
John 8:44
Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it.
Then Paul, who knew what had been taught by Jesus about men becoming devils, told Elymas the sorcerer that Elymas was a child of the devil as well.
Acts 13:10
And said, O full of all subtlety and all mischief, thou child of the devil, thou enemy of all righteousness, wilt thou not cease to pervert the right ways of the Lord?
John the Apostle lets us know again how men become children of the devil by doing unrighteousness.
1 John 3:10
In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother.
Jude also leets us know how a man becomes a devil in the following scriptures;
Jude 1:4
For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ.
Jude 1:7
Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire.
Jude 1:8
Likewise also these filthy dreamers defile the flesh, despise dominion, and speak evil of dignities.
Jude 1:12
These are spots in your feasts of charity, when they feast with you, feeding themselves without fear: clouds they are without water, carried about of winds; trees whose fruit withereth, without fruit, twice dead, plucked up by the roots;
Jude 1:13
Raging waves of the sea, foaming out their own shame; wandering stars, to whom is reserved the blackness of darkness for ever.
Jude 1:18
How that they told you there should be mockers in the last time, who should walk after their own ungodly lusts.
Jude 1:19
These be they who separate themselves, sensual, having not the Spirit.
These, who become devils, can never be saved, because they have rejected God. They will never ask for repentance, they will never have a resurrection. They would reject redemption as well as Jesus Christ as their Lord. They are EVIL.
The Pharisees were children of the devil by acceptance, they were disobedient children like Satan, so by way of behavior the accepted their progenitor, Satan, as their Father, in unrighteousness.
The devil, Satan, by process of elimination, could only be a fallen Angel, the Father of all liars, called the Serpent. Satan is a Father of all Liars, the Phariees were liars proven by scripture, they were the spiritual children of the Devil. THEY WERE DEVILS.