Investigators say they're still stumped by what drove a Florida college student to allegedly kill two strangers and eat the face of one of them in a random attack, but suspect Austin Harrouff has emerged in personal videos talking about steroids and his "psycho side."

It took a police dog, stun-gun jolts and a number of officers to subdue the "abnormally strong" suspect. Investigators said that 19-year-old Harrouff was "making animal noises" as he mauled the face of John Stevens on Monday (15 August).

The murder victim and his wife, Michelle Mishcon Stevens, had been stabbed to death in a "completely unprovoked attack", law enforcement officials added.

They don't believe Harrouff knew the couple, but happened to see the two as they sat in their re-modelled garage with the door open when he passed by them in Florida's Tequesta town.

Harrouff reportedly had a reputation as a standout high school football player and wrestler, was a good student at the Florida State University, and did not have any trouble with the law, until now.

Police suspected that he may have been under the influence of a massively powerful, transformative drug such as flakka, but thorough test results are unlikely to be available for the next few days. Initial tests found no evidence of cocaine, marijuana or heroin in his system, police said.

Harrouff is currently under guard at a Palm Beach County hospital and his condition was believed to be worsening as police feared he might not survive. However, he did not appear to be mortally wounded in any way.

Nonetheless, he is now said to be stable and is conscious after undergoing a surgery for an undisclosed injury, a spokesman for the Martin County sheriff's office told the Miami Herald.

In a number of his videos, Harrouff is seen discussing taking steroids and deciding not to do so any longer in rambling musings that sometimes slip into incoherence. The top caption of his YouTube page notes: "I've got a psycho side and a normal side. I've lost my mind help me find it."

He also appears in videos as his "alter ego" Austi Frosti and sings, including the song Devil In Disguise.

An Austi Frosti rap video posted on 11 July, titled Do You Freestyle, includes the lyrics: "I'd rather cut using a knife and slit my own throat. I'm like Bugs Bunny, I stick my teeth in because it's funny. I'm like a Looney Tune, I take a lot of 'shrooms."

Of the 54 videos he created, 41 were posted in the last month. One shows Harrouff with a knife, another with a semi-automatic pistol.

Harrouff's mother, Mina, told Jupiter investigators that her son had been acting strangely the previous week or so, and saying that he had "super powers" and was on the earth to "protect people," according to a police report on the killings. Before that, there was no indication of any violence, drug use or mental health issues, she told police.

But neighbors said they overheard several screaming fights between Harrouff and his father, who is divorced from the teen's mum.

Mina Harrouff said that the night of the killings her son stormed out of a sports bar where they were eating with some of his friends after an argument with his father. She was so concerned that she called 911 when he left. The Stevens lived nearby.

Harrouff faces charges of two counts of first-degree murder and aggravated battery on a Good Samaritan — a neighbor of the Stevens who called 911 and was stabbed several times when he tried to help the couple.

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