Kin of tragic tot tossed into East River accuses NYPD of ‘negligence’: ‘We’re devastated’

Grieving kin of a 2-year-old boy whose dad allegedly threw him in the East River are blaming cops for not stopping the slaying — even though the tot was dead before the NYPD even knew he was missing.

Law-enforcement told The Post on Monday that the mom of little Montrell Williams did not alert cops that he had vanished with his father till May 11 — the day after Arius Williams, 20, had already allegedly threw his little son off the Bruckner Bridge in The Bronx.

But still no one knew what had happened to the boy for the next two weeks — and during that time, cops botched the investigation and left the accused killer dad roaming the streets, while Montrell’s mom and other relatives were frantic with no answers, the tot’s kin said at a press conference Monday.

“A 2-year-old boy is not here today due to the neglect of the NYPD,” said the Rev. Kevin McCall, a Big Apple community activist, outside the 40th Precinct stationhouse in The Bronx. “The Police Department knew that this was a missing case, and they failed this family.”

Arius Williams is accused of tossing his son off the bridge May 10 — with the boy’s mom waiting outside a local McDonald’s on Mother’s Day the next day for her ex — who shared custody of Montrell — to drop the boy off according to their agreement. Arius never showed up with the boy.

“She didn’t hear from nobody, so she decided to call 911,” McCall said. “She called 911, and 911 told her that ‘you have to deal with this in court. This is not a police matter. It’s a custody issue matter.’

“She hung up in disbelief,” he said.

Unaware that her son had been killed the previous day, the frantic mom then spent the following weeks trying to get someone to pay attention to her plight, only to get the runaround, McCall told reporters.

Although the helpless toddler was dead before cops were notified, it still took until May 28 that a warrant was issued for him to produce Montrell to his mom.

Then last week, Arius allegedly snapped at his ex with a heartless taunt.

“Shut the f—k up! I threw that n—a into the river,” he allegedly told her.

On Wednesday, Montrell’s body washed up near the bridge off Ferry Point Park in Queens, with the city medical examiner still working to determine the exact cause of death.

“The cause and manner of death are pending further study following the examination last week,” the coroner said Monday. “The ID was confirmed by the medical examiner using DNA provided by the family.”

Arius Williams is charged with murder and manslaughter in his son’s death.

“I just want to get justice for my grandson,” Montrell’s grandmother, Octavia Roane, said Monday. “My daughter is supposed to graduate [from high school] this weekend, and [Montrell] was supposed to be here to see her.

“We’re sad,” she said. “We’re heartbroken. We’re devastated.”

A Police Department rep said in a statement, “The murder of Montrell Williams is an absolute tragedy, and the NYPD extends our deepest condolences to his family.

“Our detectives are always committed to conducting complete and thorough investigations, and the arrest of Arius Williams is the first step in the pursuit of justice for Montrell’s death.”