Authorities say a New Jersey man killed his girlfriend's infant baby in a "horrific and disturbing case."

Jhalil Williams, 29, of 512 South Jefferson Street, Orange, was arraigned this week on a charge of second-degree murder and first-degree assault in the death of 4-month-old Javion Durett, according to the Queens County District Attorney's Office.

“This is a truly horrific and disturbing case where a helpless 4-month-old infant was left in the care of the defendant who was the mother’s boyfriend," District Attorney Richard A. Brown said. "The alleged actions of the defendant are totally incomprehensible. He now faces serious charges that could lead to his spending the rest of his life behind bars if convicted.”

The death occurred Jan. 24.

Williams faces up to 25 years to life in prison if convicted on all charges. He next returns to court. Dec. 4.

A press release from the district attorney's office said Williams was responsible for the infant's care in his girlfriend's home in Jamaica, Queens, the night of his boy's death. Sometime between midnight and 3:18 a.m. "he inflicted abusive head trauma on the child, thereby causing his death," the release states.

It doesn't offer more specific information about the circumstances leading to the death,

But the New York Daily News reports investigators believe Williams shook the baby to death before calling 911 — after which Javion was rushed to a hospital, where doctors determined he'd been dead for hours.

Javion "was bleeding from the nose and rectum and had blood in his stool," the report says, quoting unnamed sources said. "His cloudy eyes and distended belly suggested traumatic abuse."

The Daily News report quotes NYPD Chief of Detectives Robert Boyce saying authorities awaited a medical examiner's report before investigating the death as a homicide.

When authorities asked Williams what he'd done to the baby, he shook a doll, according to the report.

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