Gilbert police say 7-year-old Clara Bergen was flown to a Phoenix hospital, where she was later pronounced dead after Sunday's accident.
They say 14-year-old Kayla Eherlico was transported by ambulance to a different Phoenix hospital for treatment of a shoulder injury.
Firefighters responded to the home around 9:30 a.m. Sunday and found both girls with head injuries.
Police spokesman Sgt. Jesse Sanger says the 14-year-old was on the wooden swing and the younger girl was standing nearby when it snapped at the base.
He says both were knocked into a swimming pool.
Police say neither girl lived at the home nor were they related.
A memorial fund has been set up in Clara's name:
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