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TEQUESTA (CBSMiami) — A man accused in a gruesome attack in which two people were killed and a man’s face was bitten off is now facing murder charges.

Austin Harrouff, 19, remains in the hospital after allegedly attacking a couple at their Tequesta home on Monday evening.

Deputies said Thursday he remained in critical but stable condition at St. Mary’s Hospital in West Palm Beach.

Once he is released, deputies say he will be arrested on various charges including first-degree murder, attempted first-degree murder, burglary and resisting an officer without violence.

Meantime, deputies are trying to find out what caused the Florida State University student, who had no priors, to take part in the gruesome, “random” attack that killed John Stevens and his wife, Michelle Mishcon.

Stevens’ daughter said she is deeply troubled by what happened.

“I’m feeling every emotion that there is out there…anger is at the top of the list at the moment,” said his daughter Ivy.

Authorities say Harrouff beat, stabbed and killed her father. When deputies arrived, they reportedly found Harrouff on top of her father, biting off pieces of his face.

A good Samaritan, Jeff Fisher, was also stabbed multiple times while trying to stop the attack. He has since been released from the hospital.

Deputies say they have requested the help of the FBI Lab to test Harrouff’s blood further for toxicology. His tests came back negative for common street drugs and methamphetamines. They have not confirmed if the drug Flakka – that causes excited delirium was in his system.

Dr. Deborah Mash is a professor of neurology at the University of Miami. She said certain illegal drugs on the market can produce behavior like that of the suspect’s.

“Some of these designer drugs can elevate a neurotransmitter called dopamine and this can lead to paranoia and psychosis,” said Mash.

Related: Family Of Couple Killed In Face-Biting Attack In Disbelief

Back to Monday evening, Harrouff was eating with his parents that evening when he got into an argument with his father – prompting him to leave. About an hour later, and a few miles away, Harrouff encountered the couple sitting in their garage.

A memorial service will be held Friday for the couple in Fort Lauderdale. The service will be at the Parker Playhouse at 1 p.m. and open to the public.

On Thursday, Harrouff’s family released a statement saying in part,

“The Harrouff family expresses their deepest sympathy for the pain and suffering caused by Austin Harrouff. The Harrouff family loves Austin as they know the Stevens and Mischcon families love John Stevens III and Michelle Mischon. There are no words we can offer to give any real comfort for this tragic loss. 

There are no words we can offer that can make up for the injury sustained by Jeff Fisher who was doing what we would want all good neighbors to do which was to try to help innocent people from being hurt or killed. 

We love our son and know that he is not the person some are making him to be for their own purposes. We will allow the full legal process to find the facts and the truth here.”