I hesitate to get involved in this thread because I don't want people to think I'm trying to defend all law enforcement. Bad cops need to be held accountable for their actions. If that means criminal charges then that is what should happen. If they need to be fired, then "offer them the opportunity to excel elsewhere". I just retired as a police officer, and I can tell you that I would have left the job sooner if I could have. My morale was pretty low, and stuff like the assumption by some that all cops are racist and/or corrupt really ground me down.
In 22 years I never shot anybody, never TASERed anybody, and pepper sprayed one drunk. I did point my firearm at a few people and put the TASER laser dot on a few as well and I had to use physical force to make some arrests. Those were situations where my training, the law, my "response to resistance" policy and common sense supported my actions.
I can try to answer some questions from a patrol officer's perspective, but I can't speak for the people involved.
As far as following someone because of prolonged eye contact? Only if they looked like they might be intoxicated or in distress. I don't know how to best describe it, but if you looked at me in my cruiser and looked worried or pleading I might look for a reason to stop you to make sure you were OK. I stopped several cars over the years for minor violations that turned out to be "rolling domestics", but in all of those situations it was a female that was making eye contact with me. A few times it was people who were lost and were afraid to flag me down and ask for directions. In all of those stops though, my approach was to walk up to the car and ask if everything was OK. I didn't ask for ID or anything, and the few times where there wasn't a more serious situation I gave a verbal warning for the stop and got the people going again ASAP. I should note that my agency runs a plate on every stop so I know if the vehicle is stolen or has warrants before the actual traffic stop. This also served to document our stops along with our dash cams.
We were just getting body cams as I retired. I would have loved to have had one to go along with my dash cam. My dash cam saved me from several false complaints, and a body cam would have been great insurance, as long as it worked. The test and evaluation versions we tried often didn't have enough storage or battery life, and some of them were difficult to activate under stress. I hope the ones they got work well.