Casa Grande man killed niece, her boyfriend before suicide, police say

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(Source: Casa Grande Police Department) (Source: Casa Grande Police Department)

Authorities have sorted out a double murder-suicide at a Casa Grande home earlier this week and say a man fatally shot his niece and her boyfriend before killing himself.

Police officers responded around 8:30 a.m. Monday to a 911 call about shots fired.

They say 56-year-old Rick Miller and 27-year-old Arielle Miller were discovered dead at the scene from gunshot wounds. 

[ORIGINAL STORY: Casa Grande PD: Early morning shooting leaves two dead, one critical]

A 31-year-old man was found alive with a gunshot wound but died on Wednesday afternoon. He was identified as Kyle Cooper.

Investigators say they've determined Miller shot his 27-year-old niece and her boyfriend before dying of a self-inflicted gunshot wound.

Police say a motive for the shootings remains unclear and the case remains under investigation.

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