The tragedy of Ashura' and the martyrdom of the companions and family members of Ahlul Bayt (a.s.) did not extend for a long time, and within this short duration of the battle, the sad event enfolded quickly. Historians do mention the first who was martyred, and the last.
There were also common combating practices, like duel fights, but what made the tragedy more severe was that none of these fighting rituals were observed. In general, it was Imam Husain (a.s.) who granted permission for the companions and members of Ahlul Bayt (a.s) to fight.
And Allah knows best.