Solved! I asked someone who has a bit more knowledge than I to come check it. There's some serious problems in the outlet I was using. Thanks for all the responses!

Good news, and thanks for reporting back. It was odd that it tripped when you turned it off. If you have any more info as to what was wrong with that outlet, please share. For example, did the problem show up with a simple receptacle tester or was it more complicated than that?

The ground and neutral had way too much voltage. There was a faulty ungrounded outlet on the back side of this outlet that was causing it, apparently.

Adding a useful tidbit here.. There are power strips/surge protectors that can detect electrical wiring faults in buildings, including the one you've discovered.

Thx for following up on it. Something we can learn from.

weebit_nutty wrote:Thx for following up on it. Something we can learn from.

+1

I'm not sure I agree that this would have been detected with a home depot receptacle tester or a surge protector/power strip. They might detect simple things like open ground and reverse polarity, but not things like a bootleg ground or (heaven forbid!) a reverse bootleg ground. Sounds like this may have been something complicated on a downstream receptacle. Old houses and houses that have seen some DIY electrical repairs often have problems that are best attended to by a licensed electrician.