Help: Water Leak from Second Floor

Woke up this morning to water leaking all over the first floor through the ceiling in our small townhome. Source was a leaking toilet tank from the second floor guest room. Must have been running at the least 10 hours.

Never dealt with anything like this before so looking for suggestions on who to call about the drywall in the ceiling to be replaced. The last thing I want to deal with is potential mold development.

Thank you.