Well, I'll tell you from what seems like the "home invasion" capital of the world -- Eastside San Jose, I would have thought 'home invasion'.
That's actually not true, but it sure 'seems' like it from the newspaper reports I've read here in the last 5 years.
My first impulse would be to suspect a 'home invasion' type of effort assuming no one could be seen thru the peephole. I also live alone & have 'kicked myself' for answering the door late at night without checking first, but having been married, I've had a sense of security that actually isn't warranted, but is there none-the-less.
Getting a homeowner to step outside of the front door would seem like a common home invasion ploy, especially if played in the wee hours when the resident could be still half-asleep, like I usual have been when I answered the door.
I have to admit that pulling the trigger is another issue, but again it depends on threats, both real & perceived, that were received prior to this event.