Why do i get random videos?

[Android Central Question]

Ok so I woke up at 7:56 and went to go through my gallery to delete some stuff and I found a video where there is this sour of a knife hitting or chopping a table in the back round along with water drops and whispering. After the whisper ends a sentence as it sounds, a light flashes on a table. I am really freaking out rn!! Please tell me what this is. And one more thing to add is my phone is always under my pillow and locked. No one knows my password exept my mom and she has been at work all night.