Melian. It looks like a missle launch gone wrong. Reminicent of the challenger explosion or the Columbia reentry. Liquid oxegen fuel tanks exploding on the way down?
Trying to figure out here this was. I can see airplane lights in the sky. To me it looks like So. California, but someone in CA would have to confirm.
https://www.space.com/32286-space-calendar.html shows recent launches. The poster should have given some context other than wonder what this is....