Why did additional states secede after the Battle of Fort Sumter?

The second group of southern states seceded after the attack at Fort Sumter. Four additional states left at this time. These states left because they had concerns about what would happen to slavery now that the fighting had begun. They waited until the Civil War began before leaving the Union.

Explanation:

it was certainly a debatable decision, mainly because it was based primarily on political - and not on legal or social - views. since the congress at that time was led by members of the republican party, and the territory that the tribes wanted to turn into an exclusively indian state was predominantly democratic, the proposal (as expressed in the constitution) did not succeed, but the constitution itself proved to be of crucial importance in the creation of the state of oklahoma, and, most importantly, it guaranteed the involvement of representatives of the indian tribes in the government of the future joint state.  

as a member of congress, i would have voted to ratify the constitution, or at least to have it tabled. ignoring it was an interested and partial decision.