The 18-year-old alleged killer faced the ACT Magistrates Court via-audio visual link from a remote room on Monday, charged with murdering a 38-year-old man in the mental health unit on Saturday night.

The teenager, from the Gungahlin suburb of Bonner, did not enter a plea or apply for bail.

Legal Aid defence lawyer Tamzin Lee provided the court with a mental health assessment report relating to the 18-year-old man, and asked that he be transferred to the Dhulwa secure mental health unit.

Special magistrate Margaret Hunter remanded the teenager in custody, marked him as a prisoner at risk, and recommended that he be assessed for admission to the Dhulwa facility in Symonston.

She also made a temporary non-publication order in relation to the identities of both the alleged killer and the 38-year-old man, following applications by Ms Lee and prosecutor Rebecca Christensen SC.

Ms Lee had argued the order should be made in relation to her client because he was "in a vulnerable state" and because his family held concerns for their safety.

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Meanwhile, Ms Christensen sought that publication of both parties' names be prohibited "pending confirmation of their status".

Ms Hunter remarked that such an order was "not usual" and stressed that it was temporary, commenting on the fact she had recently attended conferences about the importance of open justice.

The order is set to expire on December 5, the same day the teenager is due back in court.

The alleged killer, wearing a blue T-shirt and supported in court by a large number of people, attempted to address the magistrate at one stage during his brief first appearance.

This prompted Ms Lee to rise to her feet to stop him, while Ms Hunter also advised the defendant against speaking.

"I, too, would warn you," the magistrate told the teenager, noting court proceedings were recorded.

"You are innocent until proven guilty, and anything you say could be used against you."

The teenager's court appearance followed Detective Superintendent Hall O'Meagher telling reporters police had been called to the hospital's adult mental health unit just after midnight on Sunday, following reports of an altercation between two patients.

The detective, who is in charge of ACT Policing's criminal investigations, said officers arrived to find hospital staff "trying to revive and keep alive a 38-year-old man".

"Unfortunately, the efforts to keep the 38-year-old man alive were unsuccessful and he died at the scene," Detective Superintendent O'Meagher told reporters.

Police subsequently arrested the dead man's 18-year-old alleged killer, who had been "secured within a secure section of the mental health unit" before officers reached the scene.

The teenager was taken to the ACT police watch house and charged with murdering his fellow patient.

Detective Superintendent O'Meagher said on Sunday it would be "premature to confirm what injuries had occurred", but he indicated police did not believe a weapon was involved in the incident.

"It's still very early in the investigation. We're still trying to determine exactly what occurred," he said.

ACT Mental Health Minister Emma Davidson said on Sunday the situation was "very distressing" for the families of those involved, as it was for staff and other patients at the mental health unit.

"My thoughts are with the family of the deceased," Ms Davidson said.

"These sorts of incidents are also felt deeply by the health services staff who are extremely dedicated to caring for their patients, and I know many will be struggling with this news today.

"Canberra Health Services is doing everything to ensure that patients and staff within the [adult mental health unit] are supported at this time.

"As this is a matter for the police, I will make no further comment at this time."

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