Annie, exactly what broke on the toilet to do this kind of damage?
Wednesday the handle wasn't working right. Seems that my son chose to remove it and put lid on shelf. He figured he'd run to hardware today, as he forgot yesterday. So I get up and do what we do. Then pull chain. Wait to make sure chain wasn't stuck in between the 'cup'? and hole. All looked fine, at 3:30 am.
Went downstairs, made and drank some coffee. My friend, 'the agent' called at 5:06 am to see if I had coffee, 'Sure, c'mon over.' After pouring her some I went into the main floor bath, well I didn't make it there. stepping out of the kitchen, 'water.' First thought, 'damn dog.' Whoops, rippling water!

Water pouring through the vent fan. Out of electric switches. Paint already blistering.
It was about 5:15. Ran upstairs, turned off water. Called in claim before 5:30.