I think the author might need to get out more.
Would there be people, generally criminals, who would take advantage of the situation (i.e. power outage)?
Of course.
The average American? Very doubtful.
And why would the average American start shooting/killing people within 24hrs? How would they know it was a grid down event? How would anyone determine it was a grid down event? That is where I think those on the fringes in the first place might start spreading rumors or behaving badly. It is not like my elderly retired couple are going to come over and shoot me and the wife, just because the grid has been down for 24hrs.
4 or 5 days, those people who generally scoff at those who keep a well supplied pantry and have nothing but 4 or 5 days of food on hand, they might start to get desperate.
But how many of them have guns or the willingness to use them at that point? Get 2 or 3 weeks of grid down, then I could start to see it.