When you are dealing with a conflict that goes all the way back to the Fenian raids in the late 1700's with all hatred of 200 years of anger and 800 years of "occupation" on and off and bending the knee to England since 1171 tensions were bound not to die with the peace accord and in fact with some on both sides are still high now especially in the pro Britain North.
Doesn't make it right and it was a terribly sad day.