Perhaps you should say authors. What proof do you have that one person wrote this or that it came from one person's eye witness account? It is more likely, as they didn't have Word in those days, that all these accounts were collected together later well after they were made.
"In the year 38, the 12 Apostles lived as a closed corporation in Jerusalem. The Lord had entrusted their powers to them as a oneness and when Matthew took up his pen he could dare it only as its secretary.
... Matthew wrote for the Twelve when they were still together."
Eugene Rosenstock-Huessy, Fruit of Lips, page 142, Appendix 7.