I had the camera app open because I was going to take pictures, but looked away to my computer. Out of the corner of my eye I saw my phone snapping pictures, and there were photos of my face taken just then in the gallery, so I wasn't mistaken. I did immediately delete the photos without thinking though, it honestly just freaked me out. I tried to repeat what had just happened to see if it would happen it again, and it didn't. Is this just a feature on the phone? Like the camera focusing on a face looking away and automatically taking a photo? Or should I be concerned? I don't even have a stylus for the phone anymore, it broke and it's long gone.
The camera has an option to take pictures if you show your palm. Perhaps you did that.
There are also options to take a picture if you say some key words like "Smile", "Cheese", "Capture" etc.