Missing Harmony Montgomery's stepmother Kayla Montgomery allegedly told detectives in a June 3 interview that the girl's father was responsible for her death, according to New Hampshire court filings.

The state attorney general revealed Monday that Adam Montgomery, Harmony's career criminal, drug addict of a father, was being charged with murder, evidence tampering and more in the girl's death, which is believed to have occurred on Dec. 7, 2019, but went undetected for more than two years.

Adam Montgomery allegedly pummeled the little girl in the head with a closed fist on that date, New Hampshire Attorney General John Formella said at a Monday news briefing, "recklessly causing the death of Harmony Montgomery, a person under 13 years of age, under circumstances manifesting an extreme indifference to the value of human life."

The father, jailed since January on child abuse charges, faces new allegations of second-degree murder, falsifying evidence, abuse of a corpse, and witness tampering.

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The witness, according to court filings, is his now-estranged wife Kayla Montgomery, who in the same June interview told police her husband "had encouraged her on multiple occasions to lie to police about Harmony’s whereabouts, basically giving Kayla a "cover story" and telling her that as long as she stuck to the cover story everything would be OK."

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Adam Montgomery's defense asked the judge earlier this week to preclude the estranged wife's statements, accusing prosecutors of improperly delaying their disclosure by months in violation of discovery rules.

Kayla Montgomery is also facing charges in connection with the girl's disappearance, including allegedly lying to a grand jury and collecting welfare payments on the missing girl's behalf for months after her death.

Harmony’s mother, Crystal Sorey, forfeited custody rights in 2018. She reported Harmony missing in late November 2021, according to a police affidavit, after she spent almost two years trying to contact the girl’s father without success. When investigators began looking for her, they discovered no one they interviewed had "physically seen her" since just after Thanksgiving in 2019.

Investigators in August announced that they would shift the focus of their investigation from a missing person to a homicide – and said they believe she had been murdered in Manchester in 2019.

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Her father is an ex-con heroin addict who shot a man in Massachusetts in 2014 and is a suspect in an unrelated cold case murder.

Judge Amy Messer last week ruled on a series of motions from Adam Montgomery’s defense team alleging that his Miranda rights had been violated by a Manchester detective after his arrest. She partially granted a request to suppress his interview, ordering that only a portion conducted after the alleged violation be struck. A separate motion to suppress phone evidence was denied, with Messer finding that Adam Montgomery gave up his right to privacy when he claimed to detectives that the phone wasn't his.

He is accused of giving his partially blind daughter a black eye in 2019 and other child abuse, according to investigators.

Harmony's remains have not been found.

Anyone with information on the case is asked to call the dedicated tip line at 603-203-6060.