I like the first idea: call 911, . . . keep them on the line, . . .
Next question: is it in town where LEO response is within a few minutes? OR is it out in the boonies where LEO response may be 30 minutes from now?
Each has it's own set of baggage. In town, . . . I would probably shout at the couple to try to find out if it is some kind of kinky hanky panky and if it was, . . . I'd tell the 911 operator. Other than that, . . . I would probably just try to be a good witness, . . . I would not want to be standing in the local park with my 1911 pointed at someone when the boys in blue come storming in. In my three local towns, . . . that would be at most only a couple of minutes from the time I told the 911 operator.
Boonie land would probably cause me to not only shout, . . . but unholster in case bg decides I spoiled his party and he wants a piece of me now. He in all probability will try to zip and run, . . . most rapists are feral cowards. Have to play it by ear for what happens next.
May God bless,
If you can breathe, . . . thank God!
If you can read, . . . thank a teacher!
If you are reading this in English, . . . thank a Veteran!