The Standard Hotel said the person had been terminated for "breaching the security policies of the hotel and recording the confidential CCTV video."
The hotel said after the video was first aired that it was "shocked and disappointed" by the security breach. It said Wednesday that it will turn over "all available information to criminal authorities."
The black and white video has no audio -- but shows Beyonce's sister kicking and hitting Jay Z in an elevator of The Standard Hotel. The group appears to be wearing outfits for an after-party following the glamorous Met Gala in New York on May 5.
It's not clear what provoked the incident, but the video shows a guard trying to restrain the clearly upset 27-year-old singer, whose 32-year-old megastar sister Beyonce stood by and large in the corner alongside her 44-year-old husband of six years.
The Met Gala after-party took place at The Standard's exclusive rooftop lounge -- better known among New York night owls as "the Boom Boom Room."
The mystery employee filmed footage of a violent scuffle between Solange and Jay Z that appeared on the hotel's security feed, then promptly sold it to gossip site TMZ for a reported $250,000. TMZ then posted it on their web site -- which started the media frenzy that led the hotel to search for who leaked the video.