Family members claim 19-year-old Austin Harrouff, a student-athlete and rising sophomore at Florida State University, had been behaving strangely for weeks before the night he allegedly stabbed Michelle Mishcon Stevens, 53, and John Stevens III, 59, to death at their home near Jupiter, Florida.

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Investigators later determined Harrouff did not know the victims.

On August 15, 2016, Authorities were summoned to the Stevens’ residence following a 9-1-1 call from Jeff Fisher, the couple’s friend and neighbor. After they arrived, sheriff’s deputies allege they found Harrouff on top of Mr. Stevens, biting his face and abdomen. Reportedly, it took multiple officers, a stun gun, and a K9 unit (police dog) to subdue him. Authorities said at the time, they suspected Harrouff had been under the influence of a psychoactive stimulant, the synthetic drug known as “Flakka” on the streets.

In an exclusive interview with Dr. Phil conducted just days following the Stevens’ deaths, the accused man’s father, Dr. Wade Harrouff, adamantly denied his son was under the influence of any drug that night. Toxicology results later reportedly confirmed the assertion that Harrouff was not under the influence of any hallucinogen on the night of the attack.

Claiming his son had been behaving bizarrely for weeks, Dr. Harrouff said, “I just thought he’d snap out of it. That’s the beginning of the psychosis – he started getting weird.”

Harrouff’s father also discussed his son’s behaviors on the night of the killings - including allegedly drinking a large amount of Wesson oil and disappearing from a family dinner at a local restaurant.

Following the deaths of Michelle and John Stevens, Austin Harrouff was hospitalized for weeks before being charged with the double homicide. Dr. Phil spoke with the accused man just days prior to his being transferred to jail. That exclusive interview will air for the very first time on Thursday’s Dr. Phil. Find out where you can watch here.

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