After checking it out it seemed to be bad firmware on the ssd (holding all data) but luckily it was a known issues and we could retrieve all data...
Anyway, i asked him about backups, he said sure, every day! Turned out his main application indeed made backups, to c:\backups....

So we bought a USB Drive and installed Veeam endpoint protection, running happily ever after since....
Yesterday he send me following screenshot and asked me what this message is about.... !?
http://postimg.org/image/jomkw2qeh
I called him immediately to ask if his usb backup drive was plugged in, sure he said.....
Told him to shutdown and not to touch it... When i got there i checked the usb drive on another pc and got scared. In the backup folder, apart from the backup files there was also the 3 cryptolocker files

In the meantime i checked his pc holding all data and yes, everything was encrypted, all vss windows snapshots deleted

Tried to restore all file from the veeam backup from the day before the issue and veeam could actually mount the backup, so apparently it wasn't encrypted (yet???).
After that without even trying to save data on the pc i restored from the backup and bootet his pc without issue


Will make some changes today (get rotating drive, setup eject after backup etc...) but geez..... thanks Veeam for saving my day and his business for free!