Survivors waving and crouching?

I've played a lot of DBD, and within my time playing i've come across matches where survivors will typically: turn to me, crouching up and down, and wave, and everytime it happens i genuinely don't know what to do, do they want me to kill them for free BP or something? Was there something said survivor wanted me to do that i should have? I feel bad every time i end up killing them which often i let them escape anyways or bring them to hatch.