Stardust wrote:
GoPro is more for videos, must walk around "mounted" if plan to use handfree, etc. Your situation only requires a few snaps unless you plan to comfront someone and want the video. Plus you need to remember to take camera, battery is charged, boot up, etc. Cell phones are usually with people, on in an instant, and have photo or video too.
The new GoPros have a look back feature that some people use for a dash cam. Recording is as easy as just pressing the top button As to videos, you can take 4k stills from any video you record. A chest mounted unit would be ideal for what the OP is inquiring about. Most people have their phone in their pocket with the screen locked. In the time it takes to get it out and unlocked you will lose much of the start of the encounter.