Washington, October 23 (RHC)-- A federal jury in the United States on Wednesday found four former Blackwater security guards guilty of shootings of over 30 unarmed Iraqis in Baghdad in 2007.

Nicholas Slatten was convicted of first-degree murder and the other three guards -- Paul Slough, Evan Liberty and Dustin Heard -- were found guilty of at least three counts of voluntary manslaughter.

The jury said the criminals acted wildly in the shootings on September 16, 2007, which left 14 people dead (according to some sources, 17 people died) and 20 others injured. The incident also triggered international criticism over the role of security contractors.

The four men were convicted on about 30 charges they faced. Slatten faces a life sentence for the murder charge while the other three convicted on manslaughter charges could face some 30 years in prison.

District Court Judge Royce C. Lamberth allowed the jury to announce the verdicts, which were issued after a 10-week trial and 28 days of deliberation.

According to prosecutors, Slatten viewed killing Iraqis as "payback for 9/11" and often "deliberately fired his weapon to draw out return fire and instigate gun battles." The prosecutors said that Slatten also smashed windscreens of passing cars in Baghdad.

Blackwater Worldwide, which is now known as Academi and is based in McLean, Virginia, is the most notorious private security firm that had operated in Iraq.

Many Iraqis believe the U.S. military allowed Blackwater mercenaries to commit numerous war crimes against their compatriots with impunity.