D.C. police are looking for a man who allegedly killed a woman in front of their young children in Northeast Washington.

The shooting happened in February, when Reynard Cook and Yolanda Stone got into an argument in the street while their children waited steps away inside her car, police said. The argument ended when Cook allegedly pulled out a gun and shot Stone, 31, several times. Stone had been hospitalized since that evening on Feb. 15. On Sunday, she died.

Cook has not been seen since the shooting. “We’re looking for him,” said D.C. homicide Lt. Robert Alder. “Somebody must have seen him.”

On Monday, the D.C. Medical Examiner ruled the death a homicide, and police upgraded Cook’s arrest warrant from assault with intent to kill to murder.

At least two of their children were in the car, Alder said. According to court documents, Stone and Cook had three children together. The oldest is 7.

Reynard Cook. (Metropolitan Police Department)

Stone was killed in the 3300 block of Alden Place, the same block where at one time she and Cook had lived together. It was unclear whether Cook and Stone lived together at the time of the incident.

Court records show that in one protection order Stone took out in July 2011, she said that Cook — who has depression but had not taken his medication in six months, she said — believed someone was following him and that she was seeing another man.

On July 14 at their home, Stone told officials, Cook hit her in the head. His mother tried to hold him while Stone called police, but he left before police arrived.

She also told officials that he hit her in the eye on July 19, according to court records, when she drove their children to see him while she was living with her sister. He allegedly threatened to kill her if she returned to her sister’s house, so she moved back to their home.

Court officials ordered Cook to undergo alcohol, drug and domestic-violence counseling in connection with the 2011 protection order. Several hearings were scheduled last year, but Cook repeatedly refused to show.

In another petition Stone filed, in July 2010, she said she found Cook with another woman in their basement that month. As she went upstairs, Cook allegedly punched her and slapped her in the face.

Police have followed up on several tips about Cook, 28, who has a scar on his left hand and a tattoo on his left arm. He has also used the aliases Reyvon Stone, Don Fitzgerald Hancock, and Demarko Brown, police said. He is described as 6-foot-3, 165 pounds with black hair and brown eyes.

A vigil for Stone has been scheduled for 7 p.m. Saturday at Spingarn High School in Northeast.