The twisted Staten Island teen accused of killing his mother’s boyfriend allegedly gave a full, gory confession — including that he planned to liquify the body in a blender and flush it down the toilet, starting with the brain, law enforcement sources said.

Damien Hurstel, 19, allegedly calmly admitted to cops at the NYPD’s 120th Precinct that he fatally bludgeoned Anthony Casalaspro, 45, over the head with a meat tenderizer because he wanted to know what it was like to kill someone, sources told The Post.

Hurstel was expected to be arraigned Wednesday morning on murder and criminal possession of a weapon charges, authorities said.

Damien Hurstel, 19, allegedly calmly admitted to cops that he fatally bludgeoned the 45-year-old sanitation worker over the head with a meat tenderizer. Luiz C. Ribeiro for New York Post

The alleged spare-no-details confession came after cops took Hurstel, who has a long history of mental illness, into custody Monday evening. Facebook/Gabriella Ali Zayas

The victim has been identified as Anthony Casalaspro. Facebook/Anthony Casalaspro

The alleged spare-no-details confession came after cops took Hurstel, who has a long history of mental illness, into custody Monday evening, according to the sources.

Hurstel allegedly told police the brutal slaying unfolded after he argued with his mother during the morning inside their West Brighton home, prompting Casalaspro to tell him to take a walk to calm down, the sources said.

The agitated Hurstel allegedly returned home to find his mother gone, leading to an altercation that ended with him beating Casalaspro to death with a meat tenderizer, the sources said.

He allegedly planned to cut Casalaspro’s body into pieces that he’d pulverize with a blender, but ran into trouble carrying out his deranged dismemberment plan, according to the sources.

The disturbed teenage suspect was taken to the hospital and seen on Tuesday being wheeled out of an NYPD precinct on a gurney. Luiz C. Ribeiro for New York Post

A first attempt to sever Casalaspro’s head with a kitchen knife failed, prompting the sick suspect to grab a hand saw from a shed to finish the grisly job, sources said.

He then allegedly used a hammer in a failed attempt to remove Casalaspro’s brain, but he was interrupted by his younger sister arriving home from school, the sources said. 

The blood-drenched Hurstel allegedly chillingly told his sister, “I did something bad, go to your room,” sources detailed.

Hurstel allegedly beat Casalaspro to death with a meat tenderizer. Facebook/Anthony Casalaspro

Hurstel told police the slaying was after he had an argument with his mother, Alicia Zayas, in their West Brighton home. Facebook/Alicia Zayas

Hurstel in a 2018 photo with his mother, Zayas. Facebook/Alicia Zayas

But the unsettling warning went unheeded, as Hurstel’s sister followed a trail of blood to the bathroom and found Casalaspro’s dismembered body in the tub — with a spoon sticking out of the severed head’s eye socket, the sources said.

The grisly discovery prompted the girl, 16, to call her mother, who rushed to the Cary Avenue house as NYPD cops grappled with the scene, according to sources and neighbors.

“The mom, she just kept saying to her son, ‘Why would you kill him?! I still loved him!’ She was yelling, screaming from outside into the house. Where her son was,” said neighbor Jennifer Diaz, 46.

Hurstel was taken to a hospital after having a seizure on the way to a courthouse for his arraignment. Luiz C. Ribeiro for New York Post

The death of Hurstel’s mother’s boyfriend is being investigated by officials. Kyle Mazza/Shutterstock

An eerily calm Hurstel left the home with his hands up when police arrived shortly after 4:20 p.m., sources said.

Diaz said the alleged killer teen’s mom didn’t look at him as cops walked him from the house, hands cuffed behind his back and a spooky expression on his gore-streaked face.

“He had blood on his face and his Timberland construction boots, but not blood on his clothes,” the stunned neighbor said. 

“He looked relieved, no expression on his face. Blank face, but so calm. No expression. He said nothing, just very calm.”

Hurstel was taken to the hospital and was seen on Tuesday being wheeled out of the NYPD’s 120th Precinct on a gurney, still bloodied and wearing a Tyvek suit.

He had been scheduled for an arraignment, but he appeared to suffer a seizure while being transported to a Staten Island courthouse and was taken to a hospital, sources said.

Casalaspro’s body being transported from the Staten Island house. Kyle Mazza/Shutterstock

The teen has no criminal record, but his history of mental illness includes schizophrenia and self-harm going back to 2022, sources said.

The family has a history of domestic incident reports, according to sources. It’s unclear if the siblings are biologically related.

Casalaspro, a city Department of Sanitation worker, had been with the suspect’s mom for nearly six years and the couple “had their ups and downs with the kids,” his close friend Louis Ortiz told The Post Monday night.

Unidentified family members of Hurstel outside Staten Island Criminal Court. Luiz C. Ribeiro for New York Post

While the alleged killer could be “sweet as pie,” he “was always going through stuff in school — mental health issues,” Ortiz said.

Neighbor Mariano Castro, 36, said Casalaspro and his partner’s son appeared to have a normal relationship, noting he had just recently seen the two in their backyard mowing the lawn and grilling.

Screams from Hurstel’s mom rattled the normally quiet, tree-lined block as EMS arrived Monday evening, and at least one neighbor said she got sick as the headless body was carted from the home.

“‘There’s no need to go in, you can’t help him,’” the distraught mother told the first responders, Diaz said. 

“She was screaming. She said, ‘His head is in the tub. There’s nothing for you to do.’”

The mom and her family declined to comment.

Additional reporting by Amanda Woods and Patrick Reilly