Close the unit shut off valve immediately. Call a plumber. Notify Building Captain and property management company.
Water leaks have occurred in the past due to the failure of waterlines, appliances and hoses. Preventing a problem is the best course of action. It is strongly recommended to turn off the main unit shut off valve to your unit if you will be gone more than 72 hours. Save the cost of needlessly used gas by turning off the water heater.