A federal magistrate has refused to dismiss a lawsuit by the family of an Oakland woman who was killed by Emeryville police after allegedly shoplifting from a store, saying a jury could find that she posed no threat to the officer who shot her as she lay wounded on the ground.

Yuvette Henderson, 38, was shot in the head by Officer Warren Williams near a storage facility in Oakland in February 2015. A handgun she had been carrying was found 6 feet from her body.

Police said employees at a Home Depot in Emeryville reported they had tried to detain Henderson for shoplifting, but she fled. Williams and a second officer caught up to her in a parking area and told her to drop the gun she was carrying, but she refused and pointed it at them, police said. She dropped the gun after Williams shot her in the arm, but he said she raised her head and appeared to be looking for the weapon when he fired the fatal shot with a semiautomatic rifle.

One storage facility employee said Henderson’s hands were down when she first turned toward Williams and was shot in the arm, contradicting the officer’s testimony that she was pointing her gun at him, Ryu said. She said the doctor who performed the autopsy reported the bullet entered her arm from the side, despite Williams’ testimony that Henderson was facing him and coming toward him.

While Williams said he fired the fatal shot because he feared for his life, Ryu said a jury could reasonably determine “that Henderson did not pose an immediate threat to Williams because she was unarmed and wounded, and because although she had carried a gun, she had not previously fired or aimed it at him.”

She said jurors could also find that Williams, before firing, could have shouted a warning to Henderson as she lay on the ground.

The suit was filed by three of Henderson’s children. Emily Rose Johns, a lawyer for the children, said Tuesday that Ryu’s ruling “combats the narrative that police officers, when confronted by a person with a weapon, have the ability under the law to shoot and kill at will.”

Johns said Henderson had been living with her boyfriend in Oakland, raising her two youngest children, and working at local stores to support them. The case is scheduled for trial on May 15, the lawyer said.

Dale Allen, a lawyer for the officer and the city, said city officials “believed that as a matter of law, Officer Williams used lethal force as was appropriate to the threat posed by Ms. Henderson.” He said the officer expects to take the case to trial but would also consider an appeal of Ryu’s ruling.

Bob Egelko is a San Francisco Chronicle staff writer. Email: begelko@sfchronicle.com Twitter: @egelko