(CNN) -- A day after a jury deadlocked on whether Jodi Arias should be sentenced to death for the murder of her ex-boyfriend, the jury foreman described the decision process as tense and emotional.
"It was a gut-wrenching thing we had to go through, and everybody had to make their own decision," William Zervakos told ABC's "Good Morning America."
The foreman said some of the most difficult testimony to hear came from the dead man's relatives. "Until you're face to face with people that have gone through something like that, it's something that you really can't put into words," he said. "I'm 6 feet away from somebody talking about a horrendous loss, and if you can't feel that, then you have no emotion, no soul. And yet we couldn't allow ourselves to be emotional on the stand.
"We couldn't allow ourselves to show emotion, although I'm sure some came through, and I'm very, very proud of my peers and my jurors that were with us because they did a fantastic job of holding it together."
That stoicism in the face of emotional testimony disappeared in the jury room, he said.
Zervakos said the 32-year-old defendant simply did not fit his image of a murderer. "When you look at a young woman and you think of the crime, and then you see the brutality of the crime, it just doesn't wash," he said. "It's very difficult to divest yourself from the personal, from the emotional part of it."
Though the jury did not believe Arias' story that she killed Travis Alexander in self-defense, Zervakos said he believed Alexander abused her. "I'm very sure, in my own mind, that she was mentally and verbally abused," he said. "Now, is that an excuse? Of course not. Does it factor into decisions we make? It has to."
Zervakos said Arias' 18 days on the stand hurt her case. "She was not a good witness," he said. "There were so many contradicting stories."
But he expressed sympathy for her ability to endure her time on the stand. "I think the way the prosecutor was with her -- he's known for an aggressive style -- I think it was very hard, I think it would be difficult for anybody."
A retrial for the penalty phase will begin on July 18, Judge Sherry Stephens said.
Jurors had deliberated since Tuesday on whether Arias should get a death sentence for the 2008 murder.
A source with knowledge of the jury's vote said there was an 8-4 split in favor of sentencing Arias to death.
Jurors refused to talk to reporters and immediately left the courtroom.
The hung jury brought to a close a chapter in the high-profile case, which has lasted for months.
But the trial isn't over. In many states, the death penalty would be off the table if the jury couldn't agree.
In a written statement, Maricopa County Attorney Bill Montgomery said prosecutors "will proceed with the intent to retry the penalty phase."
"We appreciate the jury's work in the guilt and aggravation phases of the trial, and now we will assess, based upon available information, what the next steps will be," he said.
Emotions ran high in the courtroom as the jury's deadlock was announced. Arias appeared to be on the verge of tears. One of Alexander's sisters sobbed.
Even the voice of the normally stoic judge cracked as she dismissed jurors.
"Ladies and gentlemen, on behalf of the participants in this trial, I wish to thank you for your extraordinary service to this community," she told them. "This was not your typical trial. You were asked to perform very difficult responsibilities."
As the jury filed out of the courtroom, one juror said, "I'm sorry" to Alexander's family.
Jurors had deliberated for more than 13 hours in the penalty phase of the trial when they told the court they wouldn't be able to agree on a verdict.
On May 8, the same jurors decided in 15 hours that Arias was "exceptionally cruel" when she stabbed Alexander 29 times, slit his neck from ear to ear and shot him in the face. They pronounced her guilty of first-degree murder.
For Arias to be sentenced to death, a jury's decision must be unanimous.
If Arias is sentenced to death, she would be the fourth woman on death row in Arizona. On Tuesday, she pleaded with jurors to spare her.
She called Alexander's murder "the worst mistake" she had ever made, "the worst thing I've ever done." She couldn't have imagined herself capable of such a grisly crime, Arias told the jury.
"But I know that I was," she said. "And for that I'm going to be sorry for the rest of my life -- probably longer."
Arias was living in Yreka, California, when she met Alexander at a business convention in Las Vegas in September 2006. That November, he baptized Arias into the Mormon faith, a ceremony Arias said was followed by anal sex.
Arias became his girlfriend two months later, she testified. They broke up in the summer of 2007, and Alexander began dating other women.
In June 2008, Alexander missed two appointments, prompting friends to go to his house. They found his naked body crammed in a stand-up shower.
He had been stabbed 29 times in the back and torso and shot in the head. His throat was slit.
After her arrest, Arias told an elaborate lie about masked intruders breaking into Alexander's house and killing him before she narrowly escaped.
Relatives who spoke with police described her as mentally unstable.
The trial, which started in January, has been rife with talk of sex, lies and digital images -- among them graphic autopsy photos.
CNN's Catherine Shoichet contributed to this report.