Q: com.apple.photostream-agent taking too much space

The directory I listed in the title (com.apple.photostream-agent) has taken up over half of my hard drive space. 70GB on a 120GB HDD. It is filled with thousands of files, all titled something like "asset-3ioAK2" or "asset-4EFBJf" and all 1.2 MB. I don't have photo stream turned on in my iCloud settings and have zero idea why it would be filled like this. I don't even know what these files are it's filled with. I'm running a MBP (Retina, 13-inch, Late 2012) with OS X 10.10.5. It's taken up all my remaining hard drive space, and whenever I delete something to make room, this just fills in more taking up all available HDD space. Is it safe to just delete all these files? How do I prevent this folder from taking up all my space again?