Someone was in my Trashcan and I don't know who?

Someone today was in my family's trashcan outside. I was at school, and my mom was outside playing with the dog when she heard my trash can shut. She immediately ran inside and locked the doors. After school was out we had to go to the orthodontist to tighten my braces - when we got back we noticed garbage that was in the our trash can outside next to it. We waited until dad got home from work to do anything. Once he got home he checked the trash can to see if anything was in there. He thought it was a dead animal or something, I personally thought it was a body - but it turns out nothing was there. But if they didn't put anything in the trash can then why were they taking stuff out and leaving my trash to the side of it? I'm kinda freaked out and I don't know what to do.