How to permanently delete photos off my Mac?

I have recently uploaded large video files (20gb) off my old iPhone 6 to "photos" on my Mac(my iPhone runs iOS 10 I think and can't simply create "folders"). Once uploaded to "photos" on my Mac I export them to an external storage device. I delete them from the "library" and "recently deleted" section in "photos". However, after deleting them from "recently deleted" I can see they are some how moved to somewhere in "other" on my mac as the "other" section in my storage balloons from 30gb to 50gb. Does anyone know where these are going/ how to actually get rid of them?