unflagging

I come home to find 2 dog biscuits left on my doorstep, right next to my doormat. It has happened twice now, with different brands of biscuits. This is not from a dog, as they are intact and dry. Plus, what dog would leave his food somewhere? This is bizarre, and I want to know who is doing it. Can you help me get an affordable camera system? I do have a laptop, if that is necessary. I will try to position the camera in a few spots, to see which is best. Maybe on the handrail so I can see him coming up the driveway (and maybe get a shot at the license place) Or maybe not driving at all, and he's walking to my home? I can try to capture the face by mounting it above the door. Or should I mount it inside and point it out the side window. Maybe I need two cameras, to get the car and the face? I don't want to spend a ton on this, but I'd like to get to the bottom of this. Can you point me in the right direction for what to buy? I am also in the process of getting a shotgun this weekend. If I can get the footage, I can then give this to the police, in case something happens in the future.

Pretty sure it was the mailman. He must think this is the 1950s. Idiot

Where can I buy one? Got a link?