Order the building close until further notice. Let no one new in. No food deliveries, etc. Tell them if they want to leave, that is fine.
After they are all gone, reopen the building. If they do it again, repeat the process. Do not let large numbers of people in the building. I’m sure there are fire laws.
Why not turn down the heat and turn off all the hot water.
“I’m sure there are fire laws.”
Bingo!