That is media hype from 1861 to inflame northern draftees, and you still fall for it 145 years later. Who fired first was not the determinant of war.
War did not follow after South Carolina seceded on December 20, 1860.
War did not follow after Major Anderson removed his troops from Ft. Moultrie to Ft. Sumter, and turned UNION guns on the city.
War did not follow after the Union garrison fired on Florida state troops in Barrancas Barracks in Pensacola Bay, late at night on the eighth of January (the day before the Star of the West would be fired on at Charleston).
War did not follow the next day when the Star of the West, rented by the Federal government to carry troops into Charleston Harbor for purposes of conflict, was fired upon and driven off the harbor.
War did not follow during the next three months while the seceded states reclaimed their property.
There are all sorts of examples throughout history of skirmishes and fire fights that did not bring all out war.
Specifically, in Charleston the Confederate garrison did not have the power to bring war. It had the power to defend the harbor, which is what it did.
War did not follow after the Confederate garrison repelled the Union fleet attempting to enter the harbor by reducing Ft. Sumter.
It was only after Lincoln called up the state militias, ordered the blockade of Southern ports, and prepared to send Union troops into Virginia that war began. The United States government formally determined this event as the beginning of the war.
But...but...Wait -- Didn't you learn the simple history lesson that Fort Sumter = PEARL HARBOR??!
No, irrelevant, since for example: everyone today "gets" the idea that radical Islamists have long been "at war" against the US & western civilization, while we do very little in response.
So a state of war does not begin when we respond, but when they increase levels of violence from "provocation" to "acts of war".
Consider likewise, in WWII both Japanese & Germans committed provocations against US forces, especially by attacking navy ships, but none of these provocations rose to the level of act of war before Pearl Harbor.
So also with US Civil War.
For months secessionists provoked war with numerous acts and threats of violence against Union officials & property.
But Confederate bombardment of Union troops in Fort Sumter was their first action rising to the level of act of war.
Lincoln's initial responses were not acts of war, since, for example, calling for 75,000 troops did not even match the Confederacy's army of 100,000.
Nor is an announced blockade, by itself, necessarily an act of war, as President Kennedy demonstrated when blockading Cuba against Soviet missile-carrying ships.
A serious act of war is just what the words imply: a major military assault on another military, such as Pearl Harbor and Confederate actions against Union troops in Fort Sumter.