How is the grudge between the two families described?

In the prologue to Romeo and Juliet, the grudge or feud between the Montagues and the Capulets is described in the first four lines as such:

Two households, both alike in dignity                                                (In fair Verona, where we lay our scene),                                      From ancient grudge break to new mutiny,                                  Where civil blood makes civil hands unclean. (lines 1-4)

These four lines provide several pieces of information.  First, the line "alike in dignity" tells us that both families are of similar stature within the community of Verona.  "From ancient grudge" suggests that the feud has been ongoing for quite a while, while the reference to "new mutiny" tells us that there have been recent bouts of fighting as well.  Finally, line 4 tells us that the feud is causing citizens of Verona to spill each other's blood.