The girl was found by her 7-year-old brother on a treadmill in the Phoenix home Monday. She had been strangled by a cord connected to the machine, said Sgt. Andy Hill of the Phoenix Police Department.

"We believe the child was on the treadmill but it was not running at the time. She might have been playing like it was," Hill said.

This is why you don't let a 4 year old out of your sight.