There is a lot of debate about Peter. Some scho;ars hold that it is early, and its content comes not from eye witness accounts but from an exegetical tradition, i.e., they determined what happened from scripture (the Old Testament).Metacrock wrote:the evidence is that they are in peter and theory not coped because Peter did not copy Matthew,
Analysis reveals that the passion narrative of the Gospel of Peter has been composed on the basis of references to the Jewish scriptures. The Gospel of Peter thus stands squarely in the tradition of exegetical interpretation of the Bible. Its sources of the passion narrative is oral tradition, understood in the light of scripture, interpreted within the wisdom movement. This accords with what we know of the confessions of the earliest believers in Jesus: in the beginning, belief in the suffering, death, burial, and resurrection of Jesus was simply the conviction that all this took place "according to the scriptures" (I Cor. 15:3-5).
Ron Cameron argues that the Gospel of Peter is independent of the canonical four (The Other Gospels, pp. 77-8):
The Gospel of Peter, as a whole, is not dependent upon any of the canonical gospels. It is a composition which is analogous to the Gospels of Mark and John. All three writings, independently of each other, use an older passion narrative which is based upon an exegetical tradition that was still alive when these gospels were composed, and to which the Gospel of Matthew also had access.
You have cited Raymond Brown in this context. From what I can see, Brown, like most scholars, dates Peter to the second century, and says it depends on the earlier gospels.
In The Death of the Messiah, Raymond Brown maintains that the Gospel of Peter is dependent on the canonical gospels by oral remembrance of the gospels spoken in churches. The opinion that the Gospel of Peter is dependent upon the canonical gospels directly is also a common one.
Raymond E. Brown and others find that the author may have been acquainted with the synoptic gospels and even with the Gospel of John; Brown (The Death of the Messiah) even suggests that the author's source in the canonical gospels was transmitted orally, through readings in the churches, i.e. that the text is based on what the author remembers about the other gospels, together with his own embellishments.
Instead, following the work of Raymond Brown, Joel Green, Alan Kirk, and others, we accept the majority view that the Gospel of Peter is indeed a second-century work, literarily dependent on earlier gospel accounts.
https://books.google.co.uk/books?id=ATB ... wn&f=false
So Biblical scholarship seems divided on whether Peter depends on the canonicals or was devised from scripture. Either the guards came from Matthew or the Old Testament. And not from then actually being there.