An Idaho man is accused of killing his daughter and attacking his son in a “horrific act of family violence.”

Delbert Cornish, aged 51, faces charges of first-degree murder and aggravated assault, as indicated by court records. Currently, he is detained in the Canyon County Jail without the option of bail.

Documents from the court, as reported by local NBC affiliate KTVB, reveal that Cornish had been contemplating ending the lives of his three children and himself for almost a year, following his acquisition of a black 9 mm Hi-Point handgun in September or October of 2024. This plan came to a head on a Monday.

In a house located on the 1600 block of Blaine Street in Caldwell, a suburb near Boise, Cornish allegedly consumed several alcoholic drinks around 9 a.m., which he recounted to Caldwell police officers. He then proceeded to his 18-year-old daughter Hope Cornish’s bedroom and shot her in the head, as stated in a probable cause affidavit.

Afterwards, he kissed his daughter’s cheek and shot her cat, reasoning that no one would care for it once they were all deceased, according to the affidavit. Cornish reportedly placed a large gay pride flag over Hope’s body “as a tribute to her because it was important to her.”

As time went on, details of Cornish’s actions during those hours remain unclear, but it is noted that he awaited his son’s return from school. Upon his arrival, Cornish reportedly engaged his son, aged either 14 or 15, in a conversation about school before disclosing that “he had killed his sister” and attempted to persuade the boy to “check on his sister,” which the son refused, as per the affidavit.

The affidavit further indicates that “Delbert then went to the couch and picked up a gun,” at which point his son expressed a desire to leave. However, this move reportedly did not align with Cornish’s alleged intentions.

Delbert Cornish is said to have “shot at the ground,” blocked the doorway, and pointed the gun at his son’s chest. They fought over the gun, according to the child, with the son eventually winning control over the firearm. The teen then ran away from the house to call 911.

Caldwell police officers reported arriving at the home just after 4 p.m. on Monday. When they entered the front door, they saw a handgun magazine on the ground and a black Hi-Point handgun — without a magazine — “sitting on the couch in the living room.”

Delbert Cornish was not home, but other clues into what had happened were at the residence.

There was a “large note written on the wall” between the living room and kitchen, the affidavit said, adding that it appeared to be a possible murder/suicide note. The note allegedly included statements such as “I’m a man of my word my kids died by my hand. I’m tired of them being made fun of” and “I’m going! My kids are going with me.”

Investigators also found Hope Cornish’s body in a bedroom with a “large hatchet sticking into the exterior of the door.” Her “facial skin appeared pale” and she was “obviously dead,” the affidavit adds. Officers began looking for a vehicle “associated with Delbert” – a 2020 orange Dodge Challenger owned by his brother – and with the help of license plate reader cameras, they located it in the city of Mountain Home, about an hour southeast.

He was heading to his ex-girlfriend’s home, KTVB reported, and police said he was arrested “without incident.” Once in custody, he allegedly admitted murdering his daughter.

“I’m not gonna lie, I did it dude,” Delbert Cornish reportedly said unprompted as an officer was preparing to test him for gunshot residue (GSR). He then asked questions about the crime scene and whether investigators had found his daughter’s body, according to the affidavit. When the officer replied in the affirmative, the suspect reportedly “began to cry.”

“Delbert asked further questions about the gun and told me he should’ve shot himself, as well as said he didn’t want to shoot his son,” the document adds. “I later collected the GSR sample from each of his hands. While collecting the sample from his left hand, Delbert informed me that he shot the gun with his right hand.”

The affidavit goes on, in detail, about an alleged motive.

“Delbert admitted to me that he is an alcoholic who struggles with depression,” it states. “Delbert said he is tired of living and is tired of being ‘belittled’ by his brother, whom he his children live with. Delbert advised he is tired of his children being bullied by [his brother] and referenced named he calls them[.]”

Delbert Cornish allegedly then outlined that he wanted to kill his three children – which included a 24- or 25-year-old son – but the plan was “thwarted” when this older son violated his parole a few months ago and was sent back to prison.

“Delbert explained he wanted to kill his children along with himself because he believed nobody, especially [his brother], would take care of them once he was dead, and that they would not be able to carry on in life without him,” the detective wrote in the court document. “Because of this, he believed they would all be better off dead.”

The suspect also reportedly “said he felt remorseful” for shooting his daughter and said he didn’t hit his younger son – whom he said was his only biological child – “because of his love for him.”

Furthermore, while Delbert Cornish initially told the detective he did not try to kill himself once his younger son left, he “later stated he picked up the handgun from the ground and put his to his right temple” just to realize it would not fire.

Delbert Cornish has a preliminary hearing set for Sept. 3.

“My heart is heavy, and I am deeply saddened for the family and friends affected by this horrific act of family violence,” said Caldwell Chief of Police Rex Ingram. “I am thankful for the outstanding mutual aid and partnerships with our outside agencies who assisted with identifying and capturing this savage without incident.”