Some kind of fire lit up the sky.
I have seen facility flare stacks open up like that, but not quite that big. I was also thinking about a pipeline leak/fire or some sort of natural gas leak, maybe even a salt dome. I am not sure if those would behave like that or not. There was a natural gas salt dome leak and explosion near Brenham, TX in the early 90's that blew up with a big fuel air explosion, but it was day time so I don't know if it was that bright.