New Hampshire’s top prosecutor announced that Adam Montgomery has been charged with second-degree murder, falsifying evidence, abuse of corpse and tampering with witnesses at a news briefing Monday, roughly three years after the missing Harmony Montgomery was last seen alive.

Adam Montgomery, Harmony's father, allegedly pummeled the little girl in the head with a closed fist on Dec. 7, 2019, 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."

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.

The girl’s father, Adam Montgomery, has already been jailed since January on charges of child abuse in connection with the fruitless search for his missing daughter. He’s also an ex-con heroin addict who shot a man in Massachusetts in 2014 and is a suspect in an unrelated cold case murder.

MISSING HARMONY MONTGOMERY: MASSACHUSETTS WATCHDOG FINDS ‘MISCALCULATIONS’ PRECEDED GIRL'S DISAPPEARANCE

Undated portraits show Harmony Montgomery smiling

Harmony Montgomery, now 8, was reported missing two years after she was last seen. (National Center for Missing and Exploited Children)

In addition to allegedly killing his daughter, he is now also accused of attempting to get his estranged wife, Kayla Montgomery, to go along with his story, Formella revealed Monday afternoon.

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.

Adam Montgomery has a shaved head in new mugshot

Adam Montgomery is accused of beating his little daughter Harmony Montgomery to death months after, as a convicted felon, he convinced a family court to grant him custody. (Manchester Police)

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.

READ THE JUDGE'S ORDERS:

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

Harmony Montgomery is missing.

Anyone with information about Harmony Montgomery is asked to call the 24/7 tip line at 603-203-6060 (Manchester Police Department)

In July 2021, his mother-in-law filed for an order of protection after alleging that he showed up at her house with a knife and tapped on the window while her daughter was hiding there following the couple’s split.

The estranged wife, Kayla Montgomery, is also currently facing criminal charges after allegedly collecting welfare payments on behalf of Harmony for more than a year after she last saw the girl. She is also accused of lying to grand jury.

Harmony's dad and stepmom in mugshots

Adam Montgomery and Kayla Montgomery in booking photos after their arrests in January. (New Hampshire Attorney General's office)

MISSING HARMONY MONTGOMERY: TIMELINE OF NEW HAMPSHIRE GIRL'S DISAPPEARANCE

Harmony’s noncustodial biological mother reported her 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.

Earlier this year, detectives searched a former apartment of Adam and Kayla Montgomery and were seen carrying out evidence, including an entire refrigerator.

Harmony's remains have not been found.

Adam Montgomery latest mugshot

Adam Montgomery stood for a booking photo at the Hillsborough County House of Corrections on Jan. 5, 2022. His 7-year-old daughter, Harmony Montgomery, was reported missing a week earlier but hasn't been accounted for since 2019. (Hillsborough County House of Corrections)

CLICK HERE TO GET THE FOX NEWS APP

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