It wasn’t a warhead. It was a secondary from shelling. If you look for the other videos, there’s at least one that has audio of multiple impact detonations & flashes, followed by the secondary, largest explosion.
As as aside, the web chatter about this being a nuke is truly ignorant. Not getting into that.
LifeNews report from the site of last night’s attack and explosion, which left a HUGE crater:
https://www.youtube.com/watch?v=-C8GV63mnBU