Lightroom does not auto-import the images on the machine by itself.
You must have hit the import key by some chance and that would have imported images.
There is a preference to allow auto-import when a memory card/external device is connected but that also includes hitting import key atleast once.
That's what I thought...so maybe without realizing it, I must have hit import...but don't think so.
So later on today when I'm able, I will delete those images and try to start anew.
Here are the tutorials that you can refer to get started with import :