Pictures I didn't take have appeared in my album. How could they get there?

[AC Question]

I found some pictures I'd never seen before of my mum who passed away almost 2 years ago in the messenger folder on my phone. The pictures have been taken of images on a HP laptop screen which I don't own. I haven't had any pictures sent over Facebook or text. My phone isn't synced to any other devices and doesn't have a memory card which is where Carphone warehouse suggests they came from. Can anyone help please?

 

[B. Diddy]

Welcome to Android Central! Which messenger folder did you find the images in--the Facebook Messenger folder or the one used by the stock Messaging app? Are you saying you've never had any images sent to you via text message or Facebook Messenger, or that you've never had images of your mother sent to you?