Byron James Shepard, now a convicted murderer in the 2017 death of Tecumseh Police Officer Justin Terney, sat stoic as family members of the slain officer and others associated with Shepard's past testified Tuesday as part of the death penalty sentencing phase of his trial.

The same Pottawatomie County jury that convicted Shepard Monday of first-degree murder, deliberate intent, will decide if Shepard, 38, should receive the death penalty as punishment for his crime.

Officer Terney, 22, died March 27, 2017 from gunshot wounds he suffered following a shootout with Shepard, who was a passenger in a vehicle stopped by Terney.

Prosecutors, in presenting witnesses for this phase the trial, have pointed out Shepard's criminal history, as well as past violence and drug use, as they argue aggravating circumstances of the case.

Officer Terney's family members — two sisters and a brother — also took the witness stand and tearfully read their victim's impact statements to the jury.

Corey Terney fought emotions as he spoke of the loss of his “little brother” and best friend, saying he misses him “beyond measure.”

He told the jury how excited Terney was the day he interviewed for the Tecumseh police officer's job, saying his brother wanted to be police officer since the age of 3. He said he still can't comprehend what has happened.

“I do know that I cannot forgive the person who took my brother's life … he took my best friend,” he said.

Tonisha Rapp, Justin Terney's older sister, sobbed as she described how she watched the life drain out of her brother and the painful nightmare that ensued.

She said her brother's life was taken for no reason and he loved his job as a police officer.

“Justin died a hero,” Rapp said.

Another sister, Nicole Marks, spoke about how focused Justin Terney was on his dream job, saying that he had even acquired a puppy, Onyx, so he could train to become a K-9 officer.

“Byron Shepard ended Justin's life and his dream,” she said, adding the family is forever changed.

For the sentencing phase, prosecutors are tasked with proving aggravating circumstances as outlined in the Bill of Particulars for the death penalty, such as someone being a continuing threat to society. Other aggravators argued for this case include Terney being a peace officer, that Shepard shot and killed Terney to avoid arrest or prosecution and Shepard's previous violent felony convictions.

Two women with whom Shepard had past marital relationships were among those testifying Tuesday. Both recounted domestic abuse they suffered at the hands of Shepard, including being choked to the point of unconsciousness, with their testimony indicating Shepard was aggressive when using methamphetamine, but different when sober.

Another witness, a convicted felon wearing jail oranges, also was brought from Missouri to Oklahoma to testify about being assaulted by Shepard years ago. He told jurors Shepard beat him with a pipe or bat “from shoulder to ankle,” with documents from that case entered into evidence for this phase of the trial.

Prosecutor Pattye High told jurors there is one sentence that represents justice for this case and jail isn't an option for Shepard.

“Doing what's right isn't always easy, but it's always right,” she told the jury in her opening remarks.

The defense will present its arguments Wednesday as proceedings continue before District Judge John G. Canavan.

Public defenders, in opening remarks, told jurors they need to know more about Shepard before making a decision in this phase, saying that information offered won't be an excuse, but rather as an explanation as to what happened.

Because former Pottawatomie County District Attorney Richard Smothermon recused the office from this case, District 21 Cleveland County District Attorney Greg Mashburn and Prosecutors Pattye High and Travis White are representing the state for this trial.

Watch for updates.