(CNN) -- Donna Zovko will have to wait to travel to Falluja to see where her son died in one of the Iraq war's most infamous attacks.

Clockwise from upper left: Wesley Batalona, Mike Teague, Scott Helvenston, Jerry Zovko

"My dream was to go for the fifth anniversary, and that didn't come true," Zovko said this week while visiting friends in Boston, Massachusetts. "It's not that I'm afraid for me. But people with me on the trip would be in more danger."

Tuesday marks five years since her son Jerry Zovko and three other civilian employees of the Blackwater private security firm were ambushed in Falluja on March 31, 2004. Gunmen attacked vehicles holding Zovko, Mike Teague, Wesley Batalona and Scott Helvenston and set the vehicles on fire.

Shocking images beamed aroundthe world showed Iraqis celebrating in front of charred bodies strung up on a bridge over the Euphrates River. The remains were dragged through the streets. Donna Zovko honors her son »

"I didn't realize until way after the incident that he had been decapitated," said Helvenston's mother, Katy Helvenston-Wettengel, from her Florida home. "They cut his heart out. How can anybody be that hateful?"

To identify his body, she said, investigators had to gather DNA samples from her son's children.

A half-decade after the notorious attack, memories of the gruesome images have faded somewhat from the public eye, as the United States plans to reduce troop numbers in Iraq and a wrongful death suit brought by the four families heads to court-ordered arbitration.

The families accuse Blackwater of failing to prepare