Former Tulsa officer Shannon Kepler walks out of the courtroom as the jury leaves to deliberate on his fourth court case and fourth murder charge at the Tulsa County Courthouse on Wednesday Oct. 18, 2017. Kepler, on trial for the fourth time in the 2014 killing of his daughter’s black boyfriend, told jurors he had no choice but to shoot the young man. (Jessie Wardarski/Tulsa World via AP)

TULSA, Okla. (AP) — An Oklahoma prosecutor said Thursday that he isn’t surprised or disappointed that a jury convicted a white former police officer of manslaughter instead of murder in his fourth trial for killing his daughter’s black boyfriend.

Tulsa County District Attorney Steve Kunzweiler said he’s just relieved there was a conviction after former Tulsa officer Shannon Kepler’s three previous murder trials ended with hung juries.

“I’m just grateful that the jury gave us some finality with this verdict,” Kunzweiler said.

The jury convicted Kepler of first-degree manslaughter in the 2014 off-duty fatal shooting of 19-year-old Jeremey Lake, who had just started dating Kepler’s then-18-year-old daughter, Lisa Kepler. The charge carries a minimum sentence of four years in prison but sets no maximum term, leaving it up to the judge. The jury recommended that Kepler get 15 years behind bars when he’s sentenced Nov. 20.

Jurors in the first three trials deadlocked 11-1, 10-2 and 6-6, leading the judge to declare mistrials and illustrating the challenge prosecutors have in convicting a police officer, Kunzweiler said Thursday.

“In the first trial, we learned from that and realized it’s a very difficult case,” he said. “The struggle with these jurors is … can you put a police officer in prison?”

The first jury convicted Kepler of recklessly using his firearm, but it and the second jury couldn’t agree on the first-degree murder charge and didn’t have the option of a lesser charge such as manslaughter. The third jury did have the manslaughter option but found itself evenly deadlocked.

Kunzweiler said that based on interviews of some of the jurors after the previous trials, he believes some jurors allowed preconceived ideas to influence their verdicts.

“It was very obvious in some of the hung juries we had, some individuals were not doing their sworn job,” to reach a decision based on the evidence presented during the trial, he said, without elaborating on the nature of those preconceived ideas.

There was a racial undercurrent to the trials. Kepler killed Lake days before the fatal shooting of an unarmed black 18-year-old by a white police officer in Ferguson, Missouri, fanned the debate over the treatment of minorities by law enforcement.

A single black juror was seated for each of the four trials, and civil rights activists accused Kepler’s lawyers of purposely trying to exclude potential black candidates. They denied the accusation.

Kepler’s lawyers said the 24-year police veteran was trying to protect his daughter Lisa because she had run away from home and was living in a crime-ridden neighborhood. Attorney Richard O’Carroll said Lisa had been in and out of a homeless shelter since her father forbade her from bringing men into the family’s house.

Kepler, who retired from the force after he was charged, told investigators that Lake was armed and that he had shot him in self-defense, but police didn’t find a weapon on Lake or at the scene.

At his trial this week, Kepler testified that Lake made a move toward his waistband, leading him to believe he was going for a gun.

“He’s bringing it, I’m bringing it,” Kepler said. “It was either him or me. I’m not going to stand there and get shot.”

Prosecutors said Kepler first watched his daughter and Lake from his SUV before approaching them on the street. Lake’s aunt disputed Kepler’s self-defense account and has said her nephew was reaching out to shake Kepler’s hand to introduce himself when Kepler fired.

O’Carroll didn’t reply to phone messages seeking comment on the verdict.