I’ll try to keep this as simple as possible.  It may be tough to do that, because the history is so confusing due to conflicting accounts.  It all began with two quick shots right on top of each other.  Wyatt Earp claims that he fired right after Billy Clanton fired the first shot.  However, this is highly unlikely if you take Wyatt’s testimony as a whole.  Wyatt also claimed that Billy Clanton and Frank McLaury had their pistols already drawn while Wyatt did not.  If you take that as truth, it is hard to believe that Wyatt would be able to get his shot off so quickly against men who already had guns out.  Witnesses to the fight recall seeing smoke come from the front of Doc Holliday.  In fact, witnesses to the fight echo the testimonies of Billy Claiborne and Ike Clanton who stated that both Doc Holliday and Morgan Earp began the shooting.  So the real history probably has Doc Holliday shooting Frank McLaury and Morgan Earp shooting Billy Clanton.  The first two shots were followed by another quick burst of fighting.  In this fighting Tom McLaury and Morgan Earp are hit.