Genesis 3:15

15 And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.

Satan's blow to Jesus was that he was put on the cross to die for our sins. However this was not a killing blow because Jesus resurrected 3 days later as proof that He died for our sins. It was as a bruise to His heel. God's crushing blow to Satan's head will be deadly when is cast into the lake of fire forever.

In this early reference from Irenaeus circa CE 200 in which he shows that we all, both Jew and Gentile crucified Christ, he quotes the OT Psalm 2:1

Why do the heathen rage, and the people imagine a vain thing?

To show that it was Jew and Gentile who crucified Christ.

... by the mouth of our father David, Thy servant, hast said, Why did the heathen rage, and the people imagine vain things? The kings of the earth stood up, and the rulers were gathered together against the Lord, and against His Christ. For of a truth, in this city, against Thy holy Son Jesus, whom Thou hast anointed, both Herod and Pontius Pilate, with the Gentiles, and the people of Israel, were gathered together, to do whatsoever Thy hand and Thy counsel determined before to be done. Irenaeus, AH, III, XII, 5

Thus, by extension, having a hand of sorts in this, then Christ died for all.

PS The quote from Psalm 2:1 was written circa 1000 BCE, so that may be the earliest reference to our killing Jesus.

Depending upon how limited one interprets Matthew 27:25 (emphasis added)

Pilate Hands Jesus over to Be Crucified

24 So when Pilate saw that he could do nothing, but rather that a riot was beginning, he took some water and washed his hands before the crowd, saying, “I am innocent of this man’s blood;[a] see to it yourselves.” 25 Then the people as a whole answered, “His blood be on us and on our children!”

it seems to me that it could be said to be in Scripture itself.

There seems to be two distinct issues here. One is that the claim that Jesus' death was for the sins of all men. The other is related to the sense in which all men may have participated in the killing of Christ.

Universal atoning work of Christ

The atoning work of Christ was universal, in that it applied, at least in some way, to all men. There is still some debate over the extent of this topic, which would most clearly be articulated in the debate for an against "Limited Atonement" (one of the five points of Calvinism). Some would believe that the crucifixion was for only for those who would actually believe, and some would believe that it was for all, whether or not they choose to take advantage of it. Regardless, both sides still accept the relevant verses, such as:

Romans 5:18 - Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.

1 John 2:2 - And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.

The death of Christ was the death that was meant for all men, and in that sense. If it were not for our sins, Jesus would not have had to die. Consider this famous passage:

Isaiah 53:5 - But he was wounded for our transgressions, he was bruised for our iniquities: the chastis*m*nt of our peace was upon him; and with his stripes we are healed.

and in the same chapter:

Isaiah 53:11 - He shall see of the travail of his soul, and shall be satisfied: by his knowledge shall my righteous servant justify many; for he shall bear their iniquities.

That is spelled out further in the New Testament:

I Corinthians 5:21 - For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.

The picture is the same as that of the sacrifices in the Old Testament. Our sin was placed upon our Saviour. Jesus had never sinned. However, he became, in God's eyes, the very sinner that we are as our sins were placed upon him. Because God cannot tolerate sin, He had to punish that man, His own son, with the punishment that rightfully belonged to us. He was reaping the punishment that we purchased through our actions.

Therefore, in that sense, we killed Jesus. When we choose to act contrary to God's law, we are bringing down judgement upon ourselves, which God's great mercy and love demand that Christ take that punishment. So, while we aren't there literally being the executor of that judgement, since the Gospel, it has been known that we are the reason for that judgement.

There is a further sense in which a believer would at first want to accuse those who performed the crucifixion, but it becomes clear upon some reflection that were we there, just as the Jews in their hate and the Romans in their ignorance crucified Christ, we too, are just as hateful and ignorant, and in their shoes, we would have done the same thing. This theme is sometimes approached within Christian literature, but I cannot find an earliest source for this. I am not certain whether this is something that is just a universal understanding upon reflection or whether there were some original source.

Nihilism and death of morality

The author being quoted here, however, brings in another concept, one that specifically originated from a secular source, and then applying that to Christianity. He isn't quoting a terribly old concept, but one of a specific, relatively recent, concept. His approach to it is novel, but making a point that is as old as the Gospels.

The author is bringing up a reference to a work from Nietzsche titled Thus Spake Zarathustra. In it, there was a famous quote stating that God is "dead", but most people seem to miss that this was not, as is taken these days, as a statement about God or a desire for this to happen, but instead as a lament of the dangers of modern philosophies. Nietzsche championed a school of philosophy called Nihilism, which did not believe in God, nor any ultimate goal for humanity. Even though he did not believe in God, his work admitted the problem that without God, we would lack much of what makes us great. He was lamenting the fact that people, in their attempt to find naturalist answers, have removed a great advantage, even if he didn't himself believe that God existed.

From the section labeled The Madman:

God is dead! He remains dead! And we have killed him! How shall we console ourselves, the most murderous of all murderers? The holiest and the mightiest that the world has hitherto possessed, has bled to death under our knife, -- who will wipe the blood from us? With what water could we cleanse ourselves?

This isn't particularly speaking about Christianity, but of how this current world of secular reasoning was killing all gods and all morality.

Although this was a completely secular point of view, it seems to understand a bit of the truth of what we believers know from Romans:

Romans 1:18-25 - 18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness; 19 Because that which may be known of God is manifest in them; for God hath shewed it unto them. 20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: 21 Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened. 22 Professing themselves to be wise, they became fools, 23 And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things. 24 Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves: 25 Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator, who is blessed for ever. Amen.

Romans 1 deals with the nature of man and his tendency toward sin. This seems to be much of what the author quoted in the question is addressing. As men, we tend to want to fight against the Creator. We want to worship the creation instead. We ignore the very natural and obvious things that we see because we do not want to be ruled the way they tell us we should be ruled, and so we, in a figurative since, attempt to kill God in our own hearts so that we may continue to sin without a conscience.

God is the ultimate moral judge and dictator of our actions. He is the Sovereign master of each person, and when we tell him "No" or refuse to follow His orders, we are in a figurative sense putting that ruler to death in our minds and hearts. The ultimate sin is pride, and this is our tendency, to refuse God to rule as God.

Tying them together

The author is tying these ideas together in a novel way. He is taking the old literal since in which Jesus, as God and God's sacrifice, was killed because of the sin which we commit every day and showing how this is caused by the sin is the figurative sense, in which we try to put him to death in our own hearts and lives. Nevertheless, as the ultimate Lamb of God, he willingly allows this for our sakes. We, in our ignorance and sinfulness, bring death upon the Christ, but in his love and mercy, he willingly takes that death, and in exchange gives us life. We are each one of us committing this wrong, and to each one of us, hope of salvation is offered through Christ's death.

It would seem to me that the idea that Christ died for all humanity is as old as the Gospel, the idea that all humanity killed God figuratively is as old as Nietzsche, and this particular combination of the two is likely new to this article.