Refer to the below image for the locations of the open world Events. There are a total of 28 events; 17 are Drug Busts (Blue), 4 are Shoplifters (Yellow), 3 are Hit and Runs (Red) and 4 are Junk in the Trunks (Orange).
Drug Busts automatically show on your map, however the other events only show up once you get in close proximity to them. These Events also do not trigger while it is raining, or at night time. So make sure you're looking for them on a clear day.
http://images.akamai.steamusercontent.com/ugc/53063150077018...