Media Stays On Computer?

Hi. Quick question.

I am dealing with a little issue when importing video into iMovie. Not sure if it's relevent, but I'll let you know now that I am running a 15-inch Retina Macbook Pro purchased in 2013.

Essentially my issue is this:

Every time I import footage into iMovie from a camera, the footage seems to get stuck. Here is an exampleof what I mean:

Last night I imported a series of videos from my camera. My storage before import was 323GBs free. Afterwards it was 315GBs free. Once I was finished uploading to YouTube, I deleted all the files from iMovie and emptied my trash, then went and checked storage info... Still 315GBs. Checked Finder > Movies and deleted everything there too, including iMovie events. Emptied trash. Still only 316GBs available. Called Apple Tech support. They had me delete my entire iMovie library. Still didn't change anything. And yes, I have restarted the computer.

In the end, apple tech support was stumped. We just cannot seem to find where this video is hiding. I thought I would ask around here and see if anyone had experienced this problem, and knows of a fix. Really need to get that video off my computer, and free up some space considering I'm about to start off on a BIG video project and that space will fill up fast! Hopefully someone can help.

Thanks so much!

-BEE