PORTSMOUTH, Va. — A jury convicted a white former police officer of voluntary manslaughter on Thursday in the shooting death of an unarmed black man who had been accused of shoplifting.

Stephen Rankin shot William Chapman in the face and chest outside a Walmart store last year after a security guard requested that police capture the 18-year-old.

No video recorded the killing, and testimony conflicted on the details. But most witnesses said Chapman had his hands up, and prosecutor Stephanie Morales said the officer could have used non-deadly force.

The officer ‘‘brought a gun into what is at worst a fist fight,’’ Morales told the jury, which deliberated for two days before returning its verdict.

Rankin, 36, now faces one to 10 years in prison. The sentencing phase of his trial began immediately. Morales asked jurors to ‘‘give him the 10 years that he deserves.’’ Defense attorney James Broccoletti argued that incarceration would serve no purpose.

Rankin, who was fired from the Portsmouth police force after being indicted. Many in the mostly black city of 100,000 saw his trial as a chance for accountability as police shootings continue around the country.

But his lawyers said this case had nothing to do with deadly uses of force against other black men.

‘‘I think this is a terrible tragedy; I wish it had never happened,’’ Rankin testified after being found guilty. “I can’t begin to fathom how much pain that family is going through. I wish I could have done more to keep him alive.’’

Chapman’s cousin, Earl Lewis, also took the stand, to discuss the impact of his death, speaking through tears about the family’s struggle to find money to bury him.

The jurors — eight black and four white — did not convict on the first-degree murder charge prosecutors sought, but criminal charges are rare in police-involved shootings, and convictions are even more uncommon.

Broccoletti argued that Rankin had to shoot because ‘‘everything he tried to do didn’t work.’’ And some witnesses backed Rankin’s testimony. Paul Akey, a construction worker who was nearby, said Chapman ‘‘went after the officer with throwing fists, and it looked like he knocked a Taser out of the officer’s hands.’’

Rankin testified that he calmly approached Chapman to discuss the shoplifting accusation and was preparing to handcuff him when the teen refused to comply with his orders and a struggle ensued. He said he used his stun gun on him, but Chapman knocked it away.

Gregory Provo, the Walmart security guard who reported Chapman to police, testified that Chapman never charged at the officer. He said Chapman raised both hands, boxing-style, and said ‘‘Are you going to [expletive] shoot me?’’ before Rankin fired at him.