(CNN) -- Ahmad Rubaie was studying to become a doctor when his life ended seven years ago.
Ali Abdul Razzaq's life was just getting started when a bullet to the head killed the 9-year-old on September 16, 2007.
They were just two of 17 unarmed Iraqi civilians who died when four former Blackwater private security contractors opened fire at Nisur Square in Baghdad. Eighteen others were wounded.
The Iraq War incident has been a controversial political and diplomatic case from the start.
On Tuesday, a Washington jury began deliberations on whether the four guards are guilty of murder, among other charges.
The Justice Department alleges the men "unlawfully and intentionally, upon a sudden quarrel and heat of passion, did commit voluntary manslaughter."
The defendants deny all charges and say they acted in self-defense after they were fired upon by militants, but witnesses dispute the claim.
'It was horror'
Attorney Hasan Jaber was driving to work when he got trapped in traffic at the square. That's when the shooting started.
Like many others, he tried to flee, but he was shot three times.
"It was horror ... people were terrified," he said. "People running out of their cars were being shot at ... anything that moved in Nisur Square was shot. Women, children, young people, they shot everyone."
Jaber testified in Washington and said he has faith in the American justice system.
"I felt that there are people who care about this," he said. "I have trust that there will be justice."
Long road to trial
A federal judge in 2008 dismissed the original case, finding the Justice Department withheld key evidence and violated the guards' rights. But a federal appeals court later reversed that decision, leading the government to seek a fresh indictment and trial.
The incident prompted international outrage at the time, and the criminal prosecution in the United States has dragged on for years.
The killings led Iraq's government to slap limits on security contractors hired by various firms, including Virginia-based Blackwater, which is now under new management and is known as Academi.
"The vast majority of the U.S. contractors who served in Iraq did so with honor and integrity, but, as alleged today, these defendants abused their power through a relentless attack on unarmed civilians that recklessly exceeded any possible justification," said U.S. Attorney Ronald C. Machen Jr.
"This prosecution demonstrates our commitment to upholding the rule of law even in times of war and to bringing justice to the memories of those innocent men, women, and children who were gunned down in Baghdad more than six years go," he said.
CNN's Eric Marrapodi contributed to this report.