I do have a scheduled scan task set for 7pm on Wednesday nights, and when I came in this morning, ALL of my computers were shut down, even though the scan task is set to "No Action".
However, this is a different issue, so there appears to be multiple issues with shut downs happening here. This started happening before the scheduled scan ever would've triggered at 7pm. After a module update, the computers show a window with a 30 second timeout to shut down the computer!
Another user posted the window I'm talking about. See the attachment here. However, in my case, instead of "Device restart", I believe it said "Device shut down".