A Yosemite park official outlines the procedure that is being used to deal with the mice.
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An eight-year-old girl died suddenly last week after she collapsed in the classroom, suffering from a brain aneurysm.
The 72-year-old had to be helicoptered from the mountain, when he was just a few hours from the summit on Monday.
Inspectors also found the electric meter had been bypassed to avoid paying for electricity.