An Idaho man has been arrested after allegedly shooting and killing his teenage daughter. Delbert Cornish believed that he was saving his adopted daughter from being bullied and teased by killing her. Allegedly, his plan was to also kill his other children and himself, but in the end, the girl was the only one who died. Cornish allegedly confessed to killing the teen, expressing remorse for his actions. To honor her, he allegedly wrapped her in a pride flag after he killed her.
Cornish was arrested on August 18, 2025, on multiple charges, including murder and aggravated assault, KTVB reported. Around 4 p.m., officers from the Caldwell Police Department were called by Cornish’s teenage son when he escaped from their home. The teen boy told police that his father was inside with a gun. According to police, the teen said Cornish had made threats about shooting a family member.
When police made it inside the home, they found a dead woman. She was later identified as 18-year-old Hope “Onyx” Cornish. Delbert Cornish is the girl’s nonbiological father.
Police tracked Cornish and arrested him without incident about 7:30 p.m. that same day. He has been charged with murder and aggravated assault and is being held in jail without bail.
Cornish confessed to killing the girl, according to court documents obtained by Idaho News 6. “I’m not gonna lie, I did it dude,” he allegedly told a detective. The probable cause affidavit states that Cornish had previously planned to kill his children and himself.
He began to cry while being questioned, telling police he was an alcoholic who also deals with depression. The man lived with his brother and two of his children in the home where the murder took place. Cornish also told detectives he recently lost his job and had been hiding the truth from his brother until the day of the killing.
As he approached her door to kill her, Hope, who preferred to be called Onyx, opened the door. Cornish told officers he shot her in the head, standing over her body for 20 minutes watching her “gasp for breath.”
“I’m a piece of s—, man,” he allegedly said, per Idaho News 6.
Cornish then wrapped the teen in a pride flag to “honor” her, People reported, because he knew that would be very meaningful for her. The magazine also reported that in the affidavit, Cornish told police he was tired of seeing his children bullied and “belittled” by his brother. He claimed that his brother called his children names like “pedophile” and “loser.”
Onyx’s mom Crystal Thompson, spoke with News 19 about her daughter’s death. “I never, never thought that we weren’t safe physically around him,” she admitted. “We’re supposed to protect our children, not kill our children.”
Of him allegedly covering the girl in a pride flag, Thompson said it’s “not good enough for me.”
“I don’t want people to just see a name and not know who she was,” Thompson told New 19 of her daughter. “She was a fiery one. She was just very stylish, and she was kind and loving.”
A GoFundMe account has been set up to help with costs for Onyx’s celebration of life.
