They're remembering it differently. I'm not surprised. Luke wasn't there at all, Mark gets his info from Peter, I don't think Matthew supposedly went at all himself, and John was a young guy when it happened, and very old when his Gospel was written.
Essentially, not only do we have a different perspective, but we have second-hand accounts, and not only second-hand, but accounts being given several decades after the fact of an event that was very abnormal. There are actually a lot of psychology studies and experiments that test the ability of individuals to remember such details in similarly bewildering experiences. We aren't very good at it.
Do the account conflict? Yep. Absolutely. Can they be harmonized? Nope, because they are very different. However, the core message of the Gospel of the risen Christ is maintained.