Th-the strange man

A former friend of mine runs a Search and Rescue operation where we live, so a few years ago I'd sometimes help with training by hiding in the woods or some hard to reach place so one of the dogs could practice searching for live victims. He also had a dog that worked to find human remains, a dog just for rubble/dangerous ground (in the event of disaster) and he even had a bed bug dog. It was really fun and quite amazing to watch them work actually. I would also dog sit and just spend a lot of time with the dogs in general.

So, one afternoon my friend, the human remains dog, and I were just out for a walk in a pretty populated park, off duty, when a man approached us to see/pet the dog, not uncommon happened a lot especially if we were wearing our search and rescue shirts. (Quick side note: she was the most beautiful German Shepard EVER, the face of the organization and I miss her every day) The man started speaking to my friend when suddenly the dog gave her alert and indicated on the mans feet. Directly on his shoes. No question it was her signal. The man of course, didn't know that was how she indicated so he didn't notice at all as it is a subtle signal if you aren't looking for it. My friend and I looked at each other with a quick flash of unexpected horror and cut the conversation off as fast as we could and left. To this day I wonder- what the hell.

I should add that the dog would only pick of the scent of HUMAN remains. She was trained to ignore the scent of animal remains. It was my friend's gig and I was in it for the free dog love so I don't know the ins and outs of how it all worked, but I DO know her signal and she gave it- loud and clear. My friend had no explanation either and she was a VERY reliable K-9 so we don't think it was her mistake.

P.S. We took her back to the same spot to confirm it wasn't just the ground she was alerting on and she did not alert in that area again.

TL;DR My friend's trained human cadaver dog alerted on strangers feet in the park and would only do that if the scent of human remains was detected, and we still wonder WTH