I have only ever read of Josephus as being the source of an historical non Christian reference to Jesus. However, the Acts of the Apostles was written as history. Naturally it was written by believers because they were closest. When written it was history and was not a religious book. We made it a religious book.
Any reasonable historian does not reject the real existence of the man Jesus. If one rejects belief in his existence that is a matter of faith, not an acknowledgement of fact.
