This phenomenon is common enough that it has a Wikipedia entry [1].
Similar effect as "power flashes" from tornadoes; tornado blows on power lines, power lines short out, blue arc is produced, everything is bright blue for miles for a bit.
The color and sound were unlike anything I've ever seen or heard.
From memory, something like a blue'd lightning bolt without thunder + the sound of 100 giant hornets shifted down in frequency.
If you've ever seen welding light in person, imagine that intensified a couple orders of magnitude.
It looks exactly the same to my eye. https://youtu.be/q1_ZtCXLnes
That is the point.
Atlantians used it to power their space ships.
There was a large power substation about 5km away in roughly that direction, and that was my original assumption. But I don't think it tripped (at least not completely), as we didn't lose power.
It was also far brighter than I would expect from an arc at a substation (it drowned out local street lights), higher in the sky, with multiple flashes covering much more of the sky than a single substation.
So I strongly lean towards it being earthquake lights, which is a documented phenomenon.
Or, you know...UFO's.