You need to take some drywall out to see where the leak is. when you find
the leak, try to stop the leaking temporarily. (you can check how to do it
from Home Depot's website.) If you cannot do it, call 24-hour service
plumber. Usually they will do it within 24 hrs. The price may be $200 per
hour for labor charge plus parts charge.
After the plumber fix it, keep the invoice and call your home insurance
company. They will send someone to your house to check the damage.(Check
your policy)
At last, fix your dry wall and other stuffs.
Good luck.