Grandmother mourns 16-year-old girl stabbed to death in Harlem as NYPD hunts victim’s boyfriend: ‘Why would you do that?’ (EXCLUSIVE)

Cops are hunting for the teen boyfriend of a 16-year-old girl stabbed to death in a Harlem apartment, police said Monday.

Victim Saniyah Lawrence bled to death after she was stabbed in the neck in an apartment building on Adam Clayton Powell Jr. Blvd. near W. 136th St. about 5:40 p.m. Sunday.

Cops identified the suspect as Zyaire Crumbley Monday and released a photo of him. They are asking the public’s help tracking him down.

“Why would you do that?” the victim’s grieving maternal grandmother, Denise Jackson, 51, told the Daily News. “Why would you just take her life?”

The mortally wounded victim was found in an apartment after police got a 5:40 p.m. 911 call from someone in the building.

Medics rushed Zyaire to Harlem Hospital, where she died a short time later. She lived in Harlem about a mile from where she was killed.

Crumbley ran off with the murder weapon. Police said he has four prior robbery arrests, including one for which he has been on probation since May.

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The apartment where the slaying occurred is unoccupied, with different people cycling in and out, police said.

“She’s a very lovable person,” Jackson said. “Everyone that knows Saniyah would never want to hurt her because she’s not that type of person. What was the motive?”

Jackson said her granddaughter often stayed with her because Saniyah’s mother is in and out of the shelter system and her father is not around. Saniyah had been dating her boyfriend for about a year.

Zyaire like to spend time with her friends and shop. Math was her favorite subject in school, Jackson said, and she had hoped to get a part-time job in the new year.

“Put this out: we need justice for Saniyah,” Jackson said. “She didn’t deserve this.”

Anyone with information about Crumbley’s whereabouts is asked to call Crime Stoppers at (800) 577-TIPS. All calls will be kept confidential.