No. Indeed, Luke was no witness. But John was not the disciple, not a witness.... Look at how muddled his timeline of events was.
Matthew copied Mark, Q, and one other report, so he may not have been a disciple either.
But GMark was probably the memoirs of Cephas, written by the guy who followed him, ran at the arrest, etc
Mark was "probably the memoirs of Cephas"? Was that the same Cephas, who not only ran, but denied Christ 3 times after Satan had asked to sift Peter as wheat. No, relying on Mark, if indeed he was Peter's scribe, gives you no leverage. Peter was the "worthless shepherd" of Zechariah 11:16-17, who wouldn't feed, care or tend the sheep, and who was along with Paul and Judas Iscariot, the 3 shepherds of Zechariah 11:8, who were to die in the same month/generation. Peter and Paul, both the shepherds/staffs taken to "pasture" the "flock doomed for slaughter" (Zechariah 11:7), which was the Gentile church. You can always revert to the "Scripture" "which cannot be broken", the Law and the prophets. That is what Yeshua did. Of course that will leave the Gentile church in the lurch, and prepped for "YHWH's valley of judgment" (Joel 3:12 & 2).