What you have at Myrtle Beach are two biker weekends, one white (mostly) and one black. The latter has been marked by trashings, drugs and violence for so long that local merchants shutter their businesses and declare a general strike whenever it rolls around. It does not appear to be part of the sudden current urban epidemic.
The use of social media could exacerbate things at Myrtle Beach as it has elsewhere, though.
You may be mistaken about the violence at Myrtle Beach not being part of the current epidemic.
If you google “mobs Boston Charlotte Myrtle Beach” you’ll find quite a few stories about the violence. According to the articles the events were gang related and planned via Facebook to be on a day the police are already stretched to the limit.