Are we being stalked?

My sister and I are new to this town, recently we've noticed that someone has been messing around with our dog. The dog would magically disappear off the chain, and today she was placed in a way she couldn't possibly put herself in. I heard her whining and noticed that her chain was cut cleanly as if someone took a knife and cut it. My sister and I found her in a ditch in the back of our woods. The chain that she had left after it being cut was knotted onto a tree and hooked on a branch. Her collar was tightend. We have heard something similar to footsteps outside and by my window. My sister noticed that her screen would be flipped sometimes and the window would be cracked open. Tonight we we're out back and noticed the house behind the ditch (where our dog was found) a manly figure looking out the window. Are we being stalked? Or is somebody getting ready to rob us? Please help, please and thank you. We're only 16 and 17. This is recent.