A "cannibal" frat boy allegedly attacked a couple at random and chewed the dead man's face, but a toxicology report has revealed he had no hallucinogenic drugs in his system at the time.
Austin Harrouff is accused of beating and stabbing John Stevens, 59, and his 53-year-old wife Michelle Mishcon outside their home in Jupiter, Florida, on August 15.
An FBI toxicology report released on Wednesday revealed that Harrouff had no hallucinogenic drugs in his system at the time of the attacks - only a trace amount of marijuana.
Martin County Sheriff William Snyder had previously speculated that Harrouff may have been on flakka or bath salts.
The synthetic drugs have been linked to causing paranoia, nightmarish visions and periods of super-human strength, but they weren't detected in the Florida State University student.
The teenager was hospitalised for two months after the murders for a burned esophagus, possibly from ingesting chemicals found in the couple's garage.
Nellie King, Harrouff's attorney, said on Wednesday that her client is mentally ill.
"The judicial process will bear all of this out in due time," King said.
Harrouff's father, Wade, told Dr. Phil in September that he believes his son suffers from an undiagnosed mental illness, such as schizophrenia, which he says runs in his family.
Harrouff has pleaded not guilty to first-degree murder, attempted murder and burglary. He could face the death penalty if convicted. Prosecutors declined to comment.
Other pictures from the scene show a bloody knife and pair of scissors, while items of clothing and blood are also visible on the ground.
There were also picture showed splatters inside the house and in the kitchen. Another was taken in the garage when Mishcon's body was found.
Deputies had said when they arrived at the couple's home, they found the then-muscular former high school football player and wrestler in his underwear, making animal noises and biting Stevens' face as he pinned the man's body to the driveway.
According to court documents, one deputy ordered Harrouff off Stevens at gunpoint while another used an electric stun gun on him but he wouldn't let go.
Snyder has said the deputies didn't shoot Harrouff because they feared hitting Stevens.
Finally, a deputy with a dog arrived and its bites enabled deputies to subdue Harrouff. Mishcon's body was found in the garage.
Harrouff, who had no previous arrest record, told deputies: "Help me, I ate something bad."
He then admitted it was "humans" as he spit out a piece of flesh, court documents show. He begged deputies to kill him after they pulled him off Stevens, according to the records.
"Shoot me now, I deserve to die," Harrouff said.
According to police reports released Wednesday, Harrouff's family and friends told detectives he had been acting strangely in the days and hours before the attack.
His mother told police he claimed to have superpowers and having been sent to help people.
His bed had been moved to the garage because he thought there were demons in the house.
His sister, Haley, played for detectives an audiotape of Harrouff saying, "All this pain and sorrow because I solve all problems people have" and "I've become almost immortal, I have to die one day".
Haley Harrouff told detectives she had found her brother wandering the house one night saying he had the power to open locked doors.
A friend, Samuel Polacek, said Harrouff showed up at his door, asked him his birthdate and then left. He returned and they went to the beach. He said during the drive, Harrouff claimed to be half-animal, half-human.
Harrouff's father, Wade Harrouff, told investigators that they had gone for a walk the afternoon before the killings and came across two turtle shells.
He said his son pulled out a knife and said something was going to happen.
He said he convinced his son to put away the knife, which was later found near the victims. He said his son then sprinted off, but when he returned he said he was hungry so they drove to a nearby sports bar.
Wade Harrouff said that after they were seated, his son complained that the food was taking too long and left.
Harrouff apparently walked to his mother's house nearby, where she said she found him about to drink cooking oil. She said she told him to stop.
She said she soon found him eating a bowl of cooking oil mixed with cheese. After Wade Harrouff called her, she took her son back to the restaurant.
His father says that when his son returned to the table, he grabbed his son by the shirt and told him to stop acting strangely. He said his son cocked his fist but didn't swing. Instead, he left.
Surveillance video from the restaurant shows him calmly walking out about 45 minutes before the stabbings.
He apparently walked the kilometre to the victims' home, which was near his father's house. It is unknown how the encounter started, but Stevens and Mishcon were known to sit in their garage with the door open, watching television and chatting with passers-by.
The crime reports detail a fierce attack, with blood found all over the couple's driveway and their bodies displaying major wounds. Both were pronounced dead at the scene.
Harrouff's parents issued a statement days afterward expressing condolences to the Stevens family and apologising to neighbor Jeff Fisher, who was stabbed while trying to rescue the couple.