"And they all forsook him, and fled. And there followed him a certain young man, having a linen cloth cast about his naked body; and the young men laid hold on him: And he left the linen cloth, and fled from them naked." (Mark 14:50-52)
This "certain young man" is mentioned only in Mark's Gospel and was almost certainly John Mark himself. A rather obscure character in the New Testament--yet the Lord chose him to write what is probably the earliest of the gospel records of the life of Christ. If so, his account of the crucifixion and resurrection of Christ is the first record we have of the most important events in all history.
Mark's family (Acts 12:12) apparently was prosperous enough to own a home in Jerusalem with a large upper room where the disciples (even 120 of them, Acts 1:14-15) could meet for prayer after the resurrection. This was possibly the same "large upper room furnished and prepared" (Mark 14:15) where the Lord's last supper took place. Note that Mark's account says: "And in the evening he cometh |not 'goeth'| with the twelve" (v. 17). Thus Mark--probably as a teenager--was very likely an intensely interested observer of all the moving events that took place in the upper room, both before and after the crucifixion and resurrection.
He may well have overheard the conversation with and about Judas, and then watched as the disciples went out to Gethsemane. Perhaps Judas returned with the soldiers, and Mark, already in bed, grabbed a "linen cloth" and rushed out to warn Jesus. The soldiers found Jesus first, however, and Mark had to watch the disciples flee, and then finally had to flee himself.
In any case, this close proximity to these great events made such a profound impression on him that he was later led to write about them, very probably working closely with Peter (1 Peter 5:13), and Mark's Gospel was the result. HMM