CALDWELL, Idaho — A Caldwell man charged with killing his daughter in their home on Monday is being held in Canyon County custody without bail.
Delbert Cornish was arrested in Mountain Home on Monday, transferred to Canyon County custody on Tuesday, and was arraigned in Canyon County Court on Wednesday afternoon where he was appointed a public defender.
Court documents Idaho News 6 obtained through a public records request reveal many details about the case, including a confession.
WATCH: Court records reveal new details and murder confession
The records say Cornish told a detective, “I'm not gonna lie, I did it dude.” The Probable Cause Affidavit explains Cornish previously planned to kill all of his children and then himself.
Documents say Cornish began to cry while being questioned, and told officers he was an alcoholic who struggles with depression. During the interview, Cornish said he bought a gun last fall and came up with the idea to kill all three of his children and then himself, but the plan was ruined a few months ago when his oldest son violated parole and was sent back to prison.
Cornish lived with his brother and two of his children in the Caldwell home where the murder took place, just a few blocks from the Canyon County jail.
The Canyon County Coroner identified the 18-year-old victim on Tuesday as Hope Cornish. Family tells us she went by “Onyx” and that Delbert adopted her many years ago.
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Court documents show Cornish told detectives he lost his job two weeks ago but was keeping it a secret from his brother but felt he couldn’t hide it much longer. When he woke up on Monday, he told his brother, “today was the day” but did not tell him what that meant.
He walked officers through his day Monday, including how he contemplated when and how to kill Onyx. While he stood outside her bedroom door trying to decide what to do, she happened to open the door. He told officers he shot her in the head then stood there for 20 minutes watching her “gasp for breath.”
Cornish began to cry out loud and told the detective, "I'm a piece of s***, man. I'm not going to lie, I did it."
Court documents say after killing Onyx, Cornish covered her body with a Pride flag as a way to honor her, and then shot and killed her cat. He then went into a “fit of rage” and punched holes in walls around the house, and swung a hatchet into Onyx’s bedroom door. He then wrote a confession and suicide note, drank bourbon, and watched TV until his son came home from school.
Read the suspect's full confession in the probable cause affidavit below
When Cornish’s son got home, he told the teen he killed his sister and tried to convince him to go check on her. Documents say Cornish then shot the floor and pointed the gun at his son while blocking him from leaving the house. The son was ultimately able to disarm his dad, leave the house, and call 911.
Cornish then drove to his ex-girlfriend’s house in Mountain Home where he was taken into custody Monday night.
Onyx’s aunt, Debbie Duran, tells Idaho News 6 the family is devastated by this tragedy and they are currently raising money to cover funeral expenses.
Cornish will be back in court for a preliminary hearing on September 3.