You can update your "Light Locker Settings" to enforce logon and then change permissions to prevent it from being changed.
$ sudo Thunar
$ /usr/share/applications/
Right-click and change permissions for "Others:" to "None"
Mac What’s Locking File
Refer: http://apple.stackexchange.com/questions/22259/how-to-check-whats-locking-a-file
$ sudo lsof | grep -i looking-for
You will still need to kill the process and you can try the rm command too.