This article offers a few new details, and a Scribd document at the end shows the original statement of probable cause. The warning about graphic details refers to that document.

Nehemiah Griego

A statement of probable cause filed in connection with the murder of five people Saturday in the South Valley says the 15-year-old suspect initially told people at his church that his family had been killed in a car crash and were laying dead inside the home.

Bernalillo County deputies say instead that Nehemiah Griego had shot and killed his father, mother and three young siblings inside their home with weapons he found in his parent’s closet.

They say it appear the younger Griego killed his family, then drove to Calvary Church.

After hearing his stories, church officials didn’t believe him and instead called police.

[…]

Griego said he had been having homicidal and suicidal thoughts, and so around midnight on Saturday, he got a .22 caliber rifle from his parents closet and shot his mother in the head, killing her.

His nine year old brother was sleeping next to her. His brother became upset when he woke up, so Griego shot him in the head, killing him.

He said his sisters were crying and he shot both of them in the head, killing them.

Griego said he then got an AR-15 rifle from his parent’s closet and waited in a bathroom until his father arrived home at about 5 a.m. He then shot his father multiple times, killing him.

[…]

More: Probable Cause Statement Lays Out Motive and Details in Murder of Griego Family (Read the Document Below, GRAPHIC)