Around here most everyone is somewhat prepared to take care of themselves – at least for a shot time. Also almost everyone is well armed and pretty polite. At least everyone knows someone who can help arm them even if they do not have guns (the minority). I see anger on the streets as people drive.
This can change into rage if not controlled and when anger gets out of hand things might be unpredictable. In a real SHTF scenario I think those who have anger issues will get weeded out pretty quickly. “Whatever is begun in anger ends in shame.” Benjamin Franklin. As SHTF is prolonged people will band together in networks built upon relationships and referrals – family and friends being the core and starting point. We already have networks of barter and sales goring on, these will be expanded I expect.
While crime most likely will increase I do not think violence will increase greatly long term as the violence will be put down vigilante style if it begins to be a pattern (historically this has happened). This is unless some of the scenarios actually occur with an armed and organized military (our own or one allowed in). In that case we will see a tightening of non-sanctioned trade and travel, and in time will see guerrilla warfare begin. It will take some time for this to take shape as people are not prepared or trained for this unless trained by one of our militaries, but it will occur.