He was not crucified,but he watched the crucifixion of the doomed person according to the Apocalypse of Peter that was discovered in Egypt, Jesus sat on the tree and watched the crucified one getting crucified,There is a reference of that in Psalm 91:8:
You will only observe with your eyes and see the punishment of the wicked.
Peter witnessed this and wrote the Apocalypse. Not only that, but while Christians insist that the book is a Gnostic one, but according to Wikipedia "It is unclear whether this text advocates an adoptionist (Jesus was Divine) or docetist (Jesus' body and crucifixion were an illusion) christology.so there is there is no proof that the book is Gnostic.
Besides,it is not SOME who said but the Bible:
According to the books of "Acts" and "1 Peter":
29 Then Peter and the other apostles answered and said, We ought to obey God rather than men.
30 The God of our fathers raised up Jesus, whom ye slew and hanged on a tree.
31 Him hath God exalted with his right hand to be a Prince and a Saviour, for to give repentance to Israel, and forgiveness of sins.
38 How God anointed Jesus of Nazareth with the Holy Ghost and with power: who went about doing good, and healing all that were oppressed of the devil; for God was with him.
39 And we are witnesses of all things which he did both in the land of the Jews, and in Jerusalem; whom they slew and hanged on a tree:
40 Him God raised up the third day, and shewed him openly;
1 Peter 2
23 Who, when he was reviled, reviled not again; when he suffered, he threatened not; but committed himself to him that judgeth righteously:
24 Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed.
25 For ye were as sheep going astray; but are now returned unto the Shepherd and Bishop of your souls.
Others' accounts: Jesus was crucified on the cross:
39 And they that passed by reviled him, wagging their heads,
40 And saying, Thou that destroyest the temple, and buildest it in three days, save thyself. If thou be the Son of God, come down from the cross.
41 Likewise also the chief priests mocking him, with the scribes and elders, said,
32 Let Christ the King of Israel descend now from the cross, that we may see and believe. And they that were crucified with him reviled him.
And Pilate wrote a title, and put it on the cross. And the writing was JESUS OF NAZARETH ..