Mostly pilots of planes that ended up in Switzerland. Without GPS or mid-air refueling that did happen a lot. Swiss neutrality meant shooting at any military that entered their territory, no matter which side they were on, and taking anyone who surrendered captive.
Anything else could be seen as helping one side or the other, which wouldn't be very neutral. Not that they were always above helping them in non-military ways
I don't think they "shot the PoW", and I don't even know if they emprisoned them. Feels very weird how the original comment put it (why link the Swiss to the Germans like this?).
But I know that German planes ended up in the Swiss airspace. The Swiss told them to land (like "we will now escort you and you will land on our soil, and if you don't comply we shoot you down"). They refused and got shot down.
But it's very different from shooting a pilot that would be in a state of PoW.
I seem to remember that navigation systems existed during WWII for both taking bearings and computing your actual location, albeit in a wide margin of error. The British apparently jammed some well enough that Nazi pilots just landed somewhere in the Northern part of the UK
Dead reckoning while flying is hard even today. If you are flying under IMC (instrument meteorological conditions, pilot slang for "bad weather/can't see shit"), you generally have to trust that your meters and instruments are working. Without GPS (or ground based triangulation methods), you generally have to guess where you are. It's very easy to accidentally end up in a small country like Switzerland.
If anyone's looking to build a startup in aviation, try building an alternative to pitot tubes. It's pretty much the last remaining vacuum instrument that hasn't been replaced by a solid state/MEMS alternative. And vacuum instruments are about as reliable as Windows Vista.
Anything else could be seen as helping one side or the other, which wouldn't be very neutral. Not that they were always above helping them in non-military ways