A Caldwell man accused of fatally shooting his daughter earlier this week is being held in Canyon County custody without bail after court records revealed disturbing new details, including a confession.

Delbert Cornish was arrested Monday night in Mountain Home, later transferred to Canyon County custody, and formally arraigned Wednesday afternoon. A public defender was appointed to represent him.

According to a Probable Cause Affidavit obtained by Idaho News 6, Cornish admitted to detectives, “I’m not gonna lie, I did it dude.” Documents also outline a long history of troubling behavior and dark planning. Cornish reportedly told investigators that he had previously considered killing all three of his children before taking his own life, a plan he said was disrupted when his oldest son was returned to prison months ago.

The Canyon County Coroner identified the victim as 18-year-old Hope “Onyx” Cornish, who had been adopted by Delbert years earlier.

Court records state Cornish, who admitted to struggling with alcoholism and depression, recently lost his job but kept it secret from his brother, with whom he shared the Caldwell home where the murder occurred. On Monday morning, he allegedly told his brother, “today was the day,” but did not elaborate.

Cornish later described to officers how he stood outside Onyx’s bedroom door, contemplating what to do. When she opened the door, he shot her in the head and stood by for 20 minutes as she struggled to breathe. He then covered her body with a Pride flag before killing her cat and destroying parts of the home in what he described as a rage.

Investigators say Cornish wrote a suicide note, drank alcohol, and watched television until his son returned home from school. At that point, he allegedly told the boy he had killed his sister, fired a gun into the floor, and pointed it at him while trying to block his escape. The teen managed to disarm Cornish and call 911.

Cornish fled to his ex-girlfriend’s home in Mountain Home, where police arrested him later that evening.

The investigation remains ongoing as the community reels from the tragic death of Onyx Cornish.