Disturbed Staten Island teen who decapitated mom’s boyfriend told sister to ‘I did something bad’ when she arrived home to find him bloodied

The younger sister of the troubled teen accused of decapitating his mom’s boyfriend returned to her Staten Island home after school Monday to find her brother drenched in blood — chillingly telling her, “I did something bad, go to your room,” sources said.

The girl then walked into the West Brighton home and followed blood trails to the bathroom where she found the 45-year-old New York City Sanitation worker in the tub with his head removed and a knife still in his head, sources told The Post.

She then called 911.

When police arrived, the bloodied 19-year-old suspect came out with his hands up and was taken into custody. Police then located the victim, who has not yet been identified, inside, sources said.

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

The teenaged perp was taken to the hospital and has not been charged as of Tuesday morning, police said. He has no criminal history, but has a history of mental illness, including schizophrenia and self-harm going back to 2022, sources said. He has not been publicly identified.

The sanitation worker and the suspect’s mom had been together for nearly six years and “had their ups and downs with the kids,” the victim’s close friend, Louis Ortiz, told The Post Monday night.

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

Neighbor Mariano Castro, 36, said the victim and his girlfriend’s son appeared to have a normal relationship. Castro just recently saw the two in their backyard mowing the lawn and grilling.