CONCORD, N.H. (AP) — A former corrections officer was charged Thursday with second-degree murder in the death of a patient at New Hampshire’s prison psychiatric unit nine months ago.

Matthew Millar, 39, of Boscawen, is accused of kneeling on Jason Rothe’s torso and neck for several minutes on April 29 while Rothe was face-down and handcuffed in the secure psychiatric unit at the state prison in Concord. The unit treats inmates in need of acute psychiatric care, those found not guilty by reason of insanity and those — like Rothe — who haven’t committed crimes but are deemed too dangerous to remain at the state psychiatric hospital.

According to court documents, Rothe, 50, was committed to New Hampshire Hospital in 2019 because of mental illness and transferred to the prison unit in 2022 out of concern he posed a risk to himself or others. Shortly after his death, investigators said Rothe died after a physical altercation with several corrections officers and that an autopsy was inconclusive. On Thursday, the attorney general’s office said Rothe’s cause of death was combined compressional and positional asphyxia.

Millar made an initial appearance Thursday in court, where his attorney said he intends to plead not guilty. He was ordered held without bail pending a hearing Feb. 14.

Prosecutors allege that Millar acted recklessly in causing Rothe’s death after he refused to leave a “day room” in the psychiatric unit. While officers initially offered Rothe snacks and tried to talk him into leaving, they eventually decided to forcibly remove him.

In court documents, investigators said all of those involved had been trained on the use of force and interacting with inmates and patients suffering from mental illness, including specialized training about asphyxia. But the restraint Millar used is expressly contrary to that training, investigators said.

Six officers were involved in the altercation, but the attorney general’s office said it does not plan to bring further charges. Millar’s employment ended Dec. 13, the Department of Corrections said Thursday. The others had returned to work after initially being placed on leave, but they are on leave again pending another internal review, the department said.

The housing of civilly committed psychiatric patients at the prison has long sparked protest. The state has faced multiple lawsuits, and lawmakers in recent years have allocated money to build a stand-alone forensic psychiatric hospital on the grounds of the state hospital to move such patients out of the prison.