I hadn't read of this prolonged bombardment. What was their military objective in so doing? At Vicksburg, it was investment and seige, with the object of a general surrender.
Initially the firing on civilians was an attempt to force the Confederate military to give up some forts. Sounds somewhat like modern day terrorism, doesn't it. I think it eventually progressed into a general punishment of those who had the temerity to withdraw from the Union, much like Sherman's troops saved their worst for South Carolina civilians.
On August 21, 1863, Federal General Gilmore sent a communication to CSA General Beauregard demanding immediate evacuation of Morris Island and Fort Sumter or he would fire on the city within 4 hours. He sent the message at the night without his signature. He opened fire on the city about 2 AM in the morning, some 3 hours after his unsigned communique reached Beauregard's headquarters. Gillmore fired incendiary shells filled with a mixture termed "Greek Fire" after the fabled incendiary of old.
Beauregard responded, "It would appear, sir, that despairing of reducing these works, you now resort to the novel measure of turning your guns against the old men, the women and children, and the hospitals of a sleeping city, an act of inexcusable barbarity..." This went on for some days and weeks. Most of the shelling in the fall of 1863 was directed at the forts in an attempt to subjugate them, the attack on civilians not having achieved its goal. The fall shelling of the city did succeed in killing one Negro woman but I've not been able to find her name or the date of her death.
The bombardment of the forts didn't work, so Gillmore started shelling civilians again, with a particularly severe bombardment on Christmas night. Some 1,500 shells were fired on the city in 9 days in mid-January 1864. The Feds aimed at church steeples, even on Sunday mornings.
The bombardment continued day by day and month by month into 1865, sometimes heavy, sometimes light. The Charleston civilians largely moved out of the lower part of the city that Union guns could reach, but the citizens refused to yield. Finally on February 14, 1865, Beauregard ordered the evacuation of the city as his troops were needed elsewhere. Fort Sumter and other installations were evacuated by the Confederates on February 18-19. The city was looted extensively by Federal troops on February 19.
I don't know how many civilians died or were wounded in the 18-month bombardment. I've made no effort to do a thorough search in the old newspapers. I just compiled casualty reports as I ran into them.