A rookie NYPD officer will face criminal charges for the fatal shooting of an innocent man in a Brooklyn housing project, law enforcement sources said Tuesday.

Police Officer Peter Liang fired his service revolver in the unlit stairwell of an East New York apartment building Nov. 20 during a routine patrol, killing unarmed father of two Akai Gurley, 28.

Liang was indicted on second-degree manslaughter, criminally negligent homicide, assault, reckless endangerment, and two counts of official misconduct.

He is expected to surrender Wednesday afternoon, and will be arraigned in Brooklyn Supreme Court, sources said.

The top charge of manslaughter is punishable by up to 15 years behind bars.

The 27-year-old cop did not testify before the grand jury, which was convened last week, but Gurley’s domestic partner and a woman who was in the stairwell with him when he was shot both took the stand, a law enforcement source said.

The indictment pleased Gurley’s family.

“It made me so happy,” said his sister, Akisha Pringle, 19, a waitress. “I feel like my brother can rest in peace and he can know that whoever killed him . . . can get the kind of punishment they deserve.”

A source close to Liang said the officer was “shaken up” by the indictment.

Liang, who had his gun in his left hand and a flashlight in his right, has said the weapon accidentally discharged when he opened a stairwell door with the same hand that held the gun.

A neighbor said Liang has practically been a recluse since the tragedy.

“I’ve been very worried about him,” the woman said. “He’s been inside every day since the accident.”

Gurley’s sister also posted a triumphant note on Facebook.

“I Told Y’all! Now You Get What You Deserve for Your ‘ACCIDENT’. Now My Big Brother Can Rest In Peace,” Pringle wrote.

Gurley’s common-law wife, Kimberly Ballinger, who plans to sue the city for $50 million, said she was “happy” about the indictment.

Liang’s attorney, Stephen Worth, and a spokeswoman for Brooklyn DA Ken Thompson declined to comment.

Additional reporting by Larry Celona and Shawn Cohen