A Belmont woman was ordered held without bail Wednesday after she allegedly tried to kill an elderly dementia patient she knew while he was receiving treatment at a Cambridge hospital, officials said.

Tania Boghossian, 53, appeared in Cambridge District Court this week facing a charge of attempted murder. She was held without bail and ordered to undergo a mental health evaluation, according to a statement from the Middlesex County district attorney’s office.

Boghossian had allegedly been staying at a Cambridge hospital with an 80-year-old man she knew while he received treatment for complications from dementia, according to the statement.

A sitter assigned by the hospital to monitor the man reported that on Oct. 12, around 2 p.m., she heard Boghossian, who was behind a curtain in the hospital room with the man, tell him, “Take your last breath,’’ officials said.

When the sitter pulled back the curtain, Boghossian was allegedly holding a pillow to the man’s face. Hospital security was called and Boghossian was escorted out of the hospital, officials said.

Police obtained a warrant for Boghossian’s arrest after an investigation, officials said.

A spokeswoman for the district attorney’s office declined to name the hospital and to elaborate on the nature of the relationship between Boghossian and the man.

Boghossian is scheduled to appear in court again Nov. 15.

Andres Picon can be reached at andres.picon@globe.com.