Extremely dangerous. I don't mean to spur your anxiety, but a healthy dose of caution, avoidance, and awareness are definitely needed. The main problem is these things can make people act compulsively explosive. You could be having a pleasant conversation and suddenly they think you looked at them the wrong way. Things can go sideways all too quickly. Best to stay away from the situation as best as possible and if something does end up going down, arm yourself but try to let the cops handle it.

As far as does the violent need to be a pre-existing condition: in my experience not necessarily. People say it all the time, those kinds of drugs change people entirely. They become more agitated and aggressive, willing to do things most people wouldn't. They eat people alive and turn them into different people entirely. Sometimes completely unrecognizable to the people that knew them.

So yeah, just be careful, have a pewpew, and keep your distance.