I guess
jealousy was stewing for a long time.
The little girl seemed sweet, cuddly and possibly a favourite child.
PS
I'm not sure who left a "toilet flushing" note
Small children (even 7 year olds) notoriously forget to do it.
As a teacher, I should know
I guess it was a teen who left it.
(And then flew into rage when the toilet was not flushed.)
Because why should a little girl remind adults and a teen to perform such an obvious task?
I suspect serious communication problems in the family.
RIP to the victim
JMO