‘I don’t know what the f— happened’: Killer fiance who allegedly wrote ‘She must die poem’ argues with investigators who confronted him with indictment

John Carter (Butler County Prosecutor’s Office).

As seen on interrogation footage, an Ohio man argued with investigators who confronted him with a murder indictment for killing his fiancee. At the time, John Carter, 36, fervently maintained his innocence and insisted he had no idea how Katelyn Markham, 21, died years before. Or as he put it, his arms crossed: “I don’t know what the f— happened.”

A lot changed since that interrogation on March 22, 2023, in Butler County. He pleaded guilty in July 2024 to a lesser charge of involuntary manslaughter and is serving three years in prison.

Markham disappeared almost 12 years before that indictment. Carter reported her missing to 911 on Aug. 14, 2021, claiming he last saw her at her home the evening before midnight.

In April 2013, a man searching for scrap metal to sell discovered her skull in a plastic bag in an Indiana wooded area. Then other skeletal remains turned up about 30 miles from her home. Though investigators determined she died of homicide, they could not figure out her cause of death.

According to authorities, evidence against Carter included him admitting to deleting texts between him and Markham from the night of the disappearance, and also investigators noting him having scratches the day after.

Details about the long-ago case have surfaced over the years. Butler County Prosecutor Mike Gmoser said an undated typed poem found in Carter’s mother’s home suggests the “conflict and demon within” Carter, local Fox affiliate WXIX reported.

“Deep down I love her,” the poem read, according to the outlet. “You want to kill her. But I love her. She must die. I can’t kill her. Yes you can. No. Yes.”