Chilling New York City surveillance video shows a woman walk up behind a Brooklyn mom, pull out a handgun and shoot her in the back of the head on a crowded street, according to the NYPD.

Police identified the victim as Delia Johnson, a 42-year-old who can be seen leaning against a railing and talking to a group of people on a front stoop in Crown Heights in the moments before her slaying.

A police source said investigators have a possible suspect ID but have not yet made an arrest.

The video shows the assassination-style slaying of Delia Johnson.

The video shows the assassination-style slaying of Delia Johnson. (NYPD)

The video shows the assassination-style slaying of Johnson, who was struck in the back of the head, then again in the leg after she collapsed. Witnesses can be seen running for cover as the shooter gets into a white vehicle and leaves.

Police working in the area heard the gunshots and rushed to the scene, according to an NYPD source.

Officers arrived within moments and found a faint pulse and began performing CPR despite a serious gunshot wound to her head, according to the source. She was later pronounced dead at a hospital.

(NYPD)

A longer version of the video, which has not been released, shows the shooter in the area for a long period of time as people hung out on the sidewalk and near the stoops, according to the source. At one point, a man appears to hand the suspect something, which she conceals behind her back before the shooting.

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Johnson’s brother, Mathis Johnson, told the Daily News that the attacker may have followed his sister from the funeral of another neighborhood resident earlier in the day. 

"She was at a funeral earlier in the evening for an old neighborhood friend to pay her respects, and then this happened," he said. "It was horrible. That lady executed my sister."

Family members said she had a 17-year-old daughter.

(NYPD)

Police described the shooter as a dark-skinned adult female, in her mid-20s, with a heavy build and long blonde hair. She was last seen wearing a black long-sleeve shirt, black tights, a silver belt, black and white sneakers and a white purse.

Anyone with information ion the shooter is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782). 

Gun violence has soared in New York and other big cities in the year following the police-involved slaying of George Floyd in Minneapolis, which prompted protests and some violent demonstrations.

Last year, the city saw 468 murders compared to 319 in 2019, police statistics show.

So far in 2021, there were 245 as of Sunday, the most recent data available.

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City police statistics also showed more than 1,000 shooting victims in the same timeframe.

The Associated Press contributed to this report.