Right, they say almost exactly what I said above.
"MGM Resorts recently identified a cybersecurity issue affecting some of the Company’s systems. Promptly after detecting the issue, we quickly began an investigation with assistance from leading external cybersecurity experts,”
"We also notified law enforcement and took prompt action to protect our systems and data, including shutting down certain systems."
The systems are down due to MGM shutting them down, not the active attack shutting things down.