Beyonce and Jay Z looked as calm and happy as ever at the MET Costume Gala in New York City last month.
The latter's mock proposal even melted the Internet for a few hours.
But something went very wrong following this event, as TMZ has obtained surveillance footage of Solange Knowles absolutely GOING OFF on her brother-in-law inside an elevator at the Standard Hotel that same night.
It's unclear what prompted the violent attack, but Solange berates Jay Z before punching and kicking him.
Watch now as Beyonce stands idly by and a bodyguard gets in between Solange and her target, who doesn't respond in any sort of physical manner: