The station said Griego's case will go to a grand jury in 10 days.

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Nehemiah Griego, 15, will stand trial as an adult in the weekend killings, prosecutors announced.

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Nehemiah Griego, 15, tells authorities he had been having homicidal and suicidal thoughts.

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The killings had begun about four hours earlier, when Nehemiah Griego shot and killed his mother, Sarah Griego, while she slept.

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Griego told investigators he hoped to end his spree "at a Walmart, with mass destruction, " Bernalillo County Sheriff Dan Houston told reporters.

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After the slayings, Griego "spent the majority of the day with his girlfriend, " whose conduct remains a focus of the investigation, Houston said.

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The youth's father, Greg Griego, was a former pastor at an Albuquerque church and a chaplain to the city's fire department who also worked with prisoners.

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Griego told investigators he was "frustrated with his mother, " but "he did not articulate that to our investigators any further or give any explanation of that at all, " Houston said.

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Houston said the arrest came after Griego went to the family's church with his girlfriend, to whom he had sent a picture of his slain mother, and a staff member called deputies.

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For example, in the recent case of Nehemiah Griego, a 15-year-old boy accused of killing his family in New Mexico, the police seemed to have been obsessed with violent games during a press conference.

CNN: Video games didn't cause Newtown rampage