This happened to me back in May 2016 when I was visiting my parents.
It was a really nice sunny day so I decided I would drive out and visit my parents for the day. I arrived at the house and everything seemed normal. My mum was really busy that day so I said I would help her out while I was there. She asked me would I feed her cats for her so I said yes. I was looking inside the house for them but they weren't there. So I went outside and found them both within a couple of minutes. They were really lazy probably because it was such warm day that I had to feed them outside. I went back inside and got the food and fed them.
When I was walking up the steps to go back inside someone behind me shouted BOO really loud. I didn't jump nor was I afraid. I rolled my eyes at the fact that my brother or my dad was trying to scare me. I was expecting my dad or my brother to be standing behind me but when I turned around no one was there. The bathroom window was open so I thought my brother might have said it from there. I looked over at the two cats who didn't seem bothered by it at all. They were still eating their food.
In a field across from my parents house were some cows, one of the cows in particular looked terrified. I turned around again but I saw no one. I went back inside to see if anyone was in the bathroom but there was no one in there. My brother was in the sitting room the whole time and both of my parents were in the kitchen when it happened.
Whatever it was terrified the cows but I never saw it.