Jay Carciero, 37, was shot and killed by an off-duty security guard at a clinic located a few blocks away from Harvard Medical School’s Longwood campus after stabbing his psychiatrist during a treatment session.

Medical School clinical psychiatry instructor Astrid Desrosiers, 49, suffered from multiple stab wounds and was rushed to Harvard-affiliate Mass. General Hospital for treatment.

According to Boston Police Commissioner Edward F. Davis, who held a press conference to update the public following Tuesday’s incident, Desrosiers is currently in stable condition.

After hearing a woman scream in the treatment room, Paul M. Langone—a security guard not affiliated with the clinic but who happened to be nearby—burst into the room and shot Carciero three times after the psychiatric patient refused to drop his weapon.

Carciero, who had lived Reading, Mass., died from multiple gunshot wounds at Mass. General Hospital later that day.

Desrosiers had been treating Carciero for bipolar disorder.

The case is currently being investigated by the Boston Police Department, and Suffolk County District Attorney spokesman Jake Wark said that no formal charges or complaints have been made since yesterday evening.

Wark also added that investigators were pursuing “multiple avenues of inquiry,” one of which concerns Langone’s position as a special police officer—a title given to security guards authorized to carry firearms and make arrests.

Wark declined to confirm the names of parties involved or of any witnesses being interviewed in the course of the investigation.

No additional information regarding the incident has been released to the public, and spokespeople for both Harvard Medical School and Massachusetts General Hospital declined to comment.

Mass. General security director Bonnie S. Michelman praised Langone for his “heroic” actions. Michelman added that “everyone was happy he was there.”

Langone, who won the Lowell Golden Gloves boxing title 12 years ago, worked in landscaping and bar security before training to become a special officer.

Gregory M. Springer, a general manager at the Boston bar Ned Devine’s and Langone’s friend of almost 15 years, called him an “upstanding guy.”

Langone had worked at Ned Devine’s, where he served as head of security for about six years, before he made the decision to train to becomea security officer.

“I was shocked to hear about the things that happened, but it didn’t surprise me that [Langone] would be involved in a situation like this where someone needed his help,” Springer said.

“He’s very good with people and he’s a caring guy who always takes care of others,” Springer added.

Attorney E. James Perullo, who is representing Carciero’s family, told Boston radio station WBZ yesterday that he was “stunned” by the stabbing incident.

Carciero had no prior record of violence, though he had struggled with unemployment and mental health issues, according to Perullo. Carciero is survived by his wife and four children.

—Shan Wang can be reached at wang38@fas.harvard.edu.