The way I look at it, the Earps and the Cowboys were having a peen measuring contest, throwing empty threats back and forth. Then the shootout happened. Based on the testimony of witnesses, I think Billy Clanton and Frank McLaury tried to draw rather than surrender their weapons, as was the law per a city ordinance. From that point on, the Cowboys escalated it to actual violence rather than the previous back and forth. After Virgil was crippled and Morgan killed, Wyatt took things in his own hands. Can't say that I blame him, if I'm being honest.