im not in your shoes, so i cant say how i would react in your position - all i know is how i currently feel, and i currently feel that it is not a good idea to tail every person you see that looks "suspicious" ... does stuff happen? yes. but im gonna go out on a limb and say that more incidents will happen due to you following someone than if you let them be. if im walking down the street and i see some guy watching me and sneaking around following me - theres going to be a problem, even if im not up to no good....ive been held up at gun point at night before and jumped/robbed, and i saw the guys coming....i was under the mind set "nah, wont happen to me"....so i kept on about my business, and sure enough it happened....if i was in that position again, and i see someone following me or "stalking" me, as soon as they attempt to make contact with me, there will be a problem. im all for defending those around you, and defending youself, and im sorry for what happened to your friend and for the feelings of guilt you have about it, but i still believe it to be unwise to start a confrontation with somebody who may or may not be simply walking down the street. if im that worried about a shady individual, i will call the police and let them deal with it. but im not under the mindset that every black person in a hoodie is a thug, so unless i had a reason to think they were up to something (besides simply seeing them walking) i wouldnt even call the police