CALGARY -- A Calgary man found not criminally responsible for the stabbing deaths of five young adults expressed his remorse Wednesday at a review board hearing determining his future treatment and possible eventual reintegration into society.

"I am deeply sorry and regretful that my illness lead to this terrible tragedy," said Matthew de Grood, reading from a prepared statement as he sat beside his lawyer at the Alberta Review Board hearing.

"Five young people are no longer with us and their families are suffering immensely. For them, I cannot express enough my regret and sorrow for their losses. No one deserves the pain I caused. That being said, I will do everything in my power to ensure that my illness is safely managed so nothing like this ever occurs again."

De Grood had been charged with five counts of first-degree murder stemming from an April 2014 house party marking the end of the school year.

His trial was told that he heard what he thought was the voice of the devil telling him to kill and believed the end of the world was coming before he grabbed a knife from the kitchen and fatally stabbed Kaitlin Perras, 23; Lawrence Hong, 27; Josh Hunter, 23; Zackariah Rathwell, 21; and Jordan Segura, 22.

The review board consists of provincial court Judge Allan Lefever, two psychiatrists, a member of the legal community and a layperson.

They were told by de Grood's psychiatrist Dr. Sergio Santana that he is reacting well to treatment for schizophrenia and post-traumatic stress disorder.

"He made a very quick response to the psychotic medication," said Santana. "He's going back to the Matthew that he was before the illness. He has no active psychosis anymore."

But Santana cautioned there is still the possibility that his violent behaviour could return, noting his condition is only in remission. He asked de Grood be kept in custody for a full year at a psychiatric facility in Calgary so he can continue to be assessed.

Wednesday's hearing was another difficult ordeal for relatives of the victims. About 50 impact statements were filed and about 20 read aloud in court.

Lawrence Hong's father Lorenzo Hong said he fears what might happen if de Grood were ever released.

"His next logical move to eliminate this nuisance -- that means us," he said in his statement. "I can't imagine the kind of danger this will pose to us."

Kelly Hunter said since her son's death she is terrified of losing her daughter and has become an angry person, adding she believes the justice system let the families down.

"He should be put in a facility forever with no chance of release so we can try to heal from this at some point," she said.

"In my opinion, if Matthew de Grood is ever able to walk free to me it will be a huge injustice to the five innocent victims he killed. I understand he's mentally ill but no one should be put at risk by his illness again."

Kaitlin Perras's father Greg Perras said the decision that de Grood was not criminally responsible meant the families of the victims were ignored in favour of the man responsible for their deaths.

"How do you really quantify the loss of an entire life, of five lives? That is heartwrenching for me and extremely unfair to Katy, to Josh, to Zach, Lawrence and Jordan," he said.

"There must be some accountability for five lives lost and hundreds of more people affected deeply."