Open window in bathroom causes havoc

[Robyn Woods]

We get a call at 10pm on a weds night from a tenant saying that the radiator in their master bathroom has exploded open and is gushing water. We get it turned off after the entire system drains into the basement below. Plumbers come the next day and make a bypass so that heat is restored (400$ service call). Then the following Sunday morning we get a call from the same tenant that the pipes in that same bathroom but another area have busted & again water is flowing. Sunday call (500$). The plumber sends pictures of the window being left open while it’s 10 degrees outside and said that the tenant had shut off the water in the bathroom. He thinks that is what caused this whole mess. The tenant said that they opened the window because they were too hot to sleep at night. They have access to the temperature controls & we pay for the heat, so we don’t know why they didn’t turn it down besides them having new born baby exhaustion. To top it all off this happened the weekend before they are scheduled to move out. 
Could both water crisis have been caused by their open window? The 2nd certainly was. What can we reasonably hold them financially responsible for? Obviously water damage has more cost to fix than the plumber, but if we are withholding deposit funds for it we need to figure out quick what we can keep to cover this. And do we just pay for the repair to the bathroom floor, walls & basement ourselves or should they be paying for any of that too? Your insight is appreciated.