Four security contractors working for the private military firm formerly known as Blackwater have been sentenced to lengthy prison sentences for their involvement in the massacre of Iraqi civilians almost a decade ago.

A jury last year found the men guilty for their crimes and a sentencing hearing this week determined their punishment.

Paul Slough, Evan Liberty and Dustin Heard were all sentenced to 30 years and one day in prison, along with Nicholas Slatten, who was sentenced to life in prison, according to the press release from the Department of Justice. The former Blackwater employees were found guilty of killing unarmed Iraqi civilians in what has become known as the Nisur Square massacre.

The four men were part of a Blackwater armed convoy traveling through Baghdad on Sept. 16, 2007 when the group fired into the crowds, killing 14 people, including an Iraqi army soldier and two boys, aged 9 and 11. According to The Associated Press, defense attorneys argued the men fired in self-defense after being fired upon.

However, the prosecution said the men had not shown any remorse for their actions, which was an "unprovoked ambush of civilians."

The October 2014 trial found the men guilty of multiple counts of manslaughter and weapons charges. Slatten, who fired the first shot, was also found guilty of first-degree murder, according to the Justice Department.

"These sentencings are the result of the enduring resolve by law enforcement to protect victims of violent crime," said Assistant Director in Charge McCabe.

"Because this crime scene was so large and required international travel, both by witnesses and by investigators, this case required a tremendous amount of resources, time and investigative expertise. The results of this case demonstrate that the FBI will investigate violations of U.S. law no matter where they occur in order to bring justice to innocent victims."

Speaking to the court, the men continued to claim their innocence, the AP reported.

"I cannot say in all honesty to the court that I did anything wrong," Heard told the judge. But, the judge approved the sentencing.

However, there had been conflict behind the scenes between FBI investigators and Justice Department officials. Emails obtained by the New York Times reveal the two offices clashed over what charges should be levied against the men.

The FBI opted harsher charges, but in 2008 the Justice Department wanted to remove some, which would have lessened the men's punishments. These included the charge of using machine guns. At the end, it was decided to bring one charge rather than two.

Blackwater, at the time of the massacre, was one of the most influential private security contracting firms, with around $1 billion worth of government contracts. Following the massacre, it was renamed Xe Services and is now known as Academi.