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Austin Harrouff's father, Dr. Wade Harrouff, apologized for his son's alleged killings. CBS/"Dr. Phil"

Dr. Wade Harrouff, the father of the student who allegedly stabbed a married couple to death, wept for his son Thursday on the “Dr. Phil” show. Austin Harrouff, a sophomore at Florida State University, might have been under the influence of synthetic drugs when the attack happened in Florida Aug. 15-- he was still biting one of the victim’s faces when police arrived at the scene.

Some have labeled Harrouff’s son, a 19-year-old fraternity brother, a “cannibal” and “zombie.” The father called the event his “biggest nightmare.”

Before the gruesome attack, they were out to dinner as a family. Harrouff said he son was “manic” and left the restaurant to walk home. Along the way, the student stopped at the home of John Stevens and wife, Michelle Mishcon. That’s when he allegedly stabbed them to death and ate parts of Stevens’ face and abdomen.

“[Austin] would never knowingly do this,” he father said. While police mused synthetic drugs might have been involved, his father said mental illness is to blame, adding the student’s behavior changed two weeks before the assault.

“I’m deeply sorry for what my son did to those people and I apologize for him,” Harrouff told celebrity therapist Dr. Phil McGraw. “He’s such a good person. He would never knowingly do something like that. I’m truly sorry.”

Austin is currently unconscious in the hospital. He will reportedly be charged with murder when released. Though initial blood test were negative for street drugs like marijuana and cocaine, it’s unknown if he was high on flakka or bath salts.

Austin has not yet entered a plea.

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