Robert W. Funk

“The author of Mark, the earliest of the narrative gospels, was not an eyewitness: he is reporting information conveyed to him by a third person or persons, who themselves were quite possibly not eyewitnesses. (First and second persons would have been involved directly in the events being reported.) Since he doesn't name those from whom he gets his information, his sources are anonymous. The evangelist given the name Matthew reports a rumor that was circulating in his day (Matt 28:15): the guards at the tomb were bribed to say that Jesus' disciples stole his body. When the evangelist writes that the gossip was being passed around "until this very day," he is inadvertently betraying the chronological distance that separates him from events in the more remote past.”
― Robert W. Funk, The Five Gospels: What Did Jesus Really Say? The Search for the Authentic Words of Jesus