TULSA, Okla. -- An Oklahoma prosecutor said Saturday he was shocked when a judge declared a mistrial in the case of a white former Tulsa police officer who fatally shot his daughter's black boyfriend because jurors had deliberated for only a few hours.

It was the third mistrial in nine months for former Tulsa police officer Shannon Kepler, and all of the trials have been overseen by District Judge Sharon Holmes. Kepler doesn't deny shooting 19-year-old Jeremey Lake but claims he was acting in self-defense. Kepler testified Lake was armed, although police didn't find a weapon on Lake or at the scene. The shooting happened shortly after Lake had started dating Kepler's then-18-year-old daughter, Lisa.

Attorneys said jurors deliberated for just 2 1/2 to three hours Friday before saying they were deadlocked 6-6. Holmes reminded jurors the trial had started June 27 and asked whether that changed their minds. When they said no, the judge declared a mistrial.

"I have never experienced that procedure before in my life," Tulsa County District Attorney Steve Kunzweiler said, noting judges often tell juries to continue deliberating to try to reach a unanimous verdict in such circumstances.

"I was just hopeful that the court would have followed prior procedure and have the jury deliberate more," Kunzweiler said.

Tulsa County District Attorney Steve Kunzweiler addresses the media Friday after a hung-jury verdict was announced against Shannon Kepler at the Tulsa Country Courthouse.Ian Maule ~ Tulsa World via AP

The judge had told the previous juries in the case to continue deliberating after jurors reported they were deadlocked. In one case, the judge waited until 2:30 a.m. before declaring a mistrial when jurors reported they could not break their deadlock.

But defense attorney Richard O'Carroll said the procedure was not unusual and that the prosecution's case -- not the jury -- was to blame for the mistrial.

"It's frankly bad manners to blame the jury," O'Carroll said. "This thing has been sensationalized since the very beginning."

Kunzweiler said he will re-evaluate the case and decide before an Aug. 1 status conference whether to try Kepler for a fourth time. Among the factors Kunzweiler said he will consider are the prosecution and police resources required to bring Kepler to trial again.

"There's a great amount of time and effort that goes into the prosecution of these cases," he said. "Expense is a factor I'm going to have to weigh into it."

O'Carroll said it would be inappropriate to bring Kepler to trial a fourth time.

"The state's theory does not make sense," O'Carroll said. "At some stage I think the state has re re-evaluate their evidence. They threw the kitchen sink at Mr. Kepler. They got everything that they asked for."

Unlike the previous two trials, Holmes had instructed jurors they could convict Kepler of first-degree murder or the lesser charge of manslaughter. Manslaughter carries a sentence of four years to life in prison, while the sentence on a first-degree murder conviction is life in prison.

Kunzweiler said it was unclear whether the jury's deadlock was six for conviction and six for acquittal or six for murder and six for the lesser charge of manslaughter. Although previous juries could not agree on the murder charge, jurors in his first trial convicted Kepler of recklessly using his firearm.

Kepler, who retired from the force after he was charged, was a 24-year-police veteran who said he was trying to protect his daughter, who had run away from home and was living in a crime-ridden neighborhood. O'Carroll said Lisa had been in and out of a homeless shelter after her father prohibited her from bringing men into his house.

Juries in Kepler's previous two trials, in November and February, deadlocked 11-1 and 10-2 in favor of guilt before Holmes declared mistrials after up to 12 hours of deliberations in each case.

"We spent two weeks on this," Kunzweiler said. "I certainly recognize that people may have different interpretations on evidence. The goal of the system is not to have a hung jury."