DENVER -- A Vietnam War veteran who lives in Colorado offered his perspective Wednesday on the danger of friendly fire.

A Pentagon official said that an errant 2,000-pound satellite-guided bomb from an American B-52 bomber led to the death of three U.S. soldiers in a "friendly fire" incident Wednesday just north of the southern Afghan city of Kandahar.

Military officials reminded Americans that in war, there are always unexpected and unintended casualties.

It is an unfortunate reality that many Americans who have died in combat were killed by American troops or weapons in tragic accidents, 7NEWS reported.

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Hear Guerrero's Story Of Dangerous Friendly Fire

Retired Army Sgt. Artie Guerrero (pictured, left) said that he'd only been in Vietnam for a couple of months when some helicopter-fired American rockets came whistling towards him.

"I thought we were dead," Guerrero said. "To hear these rockets leave the chopper is a tremendous whining noise. Just the sound scares you."

The rockets missed Guerrero by just 20 feet.

"When you see four GIs or four long-range recon guys who've been on the road for four days already jump into one hole that's the size of maybe 2-by-2, then you understand what closeness is," he said.

Guerrero had a number of close calls. He said that bombs and missiles may be high-tech, but it's still people who decide where to aim them.

"With all that sophistication, it still doesn't make any difference. I still don't think the American people can comprehend that we're all humans," he said.

Humans make mistakes, he said. Maps and target information are occasionally wrong. In Vietnam, a shift in wind could blow munitions off course.

"That's the consequences of war. I mean, we'd like to have a perfect situation, but I'm sorry. As they would say in New York -- forget about it," Guerrero said.

Friendly fire casualties have been a part of war for centuries.

Confederate general Stonewall Jackson was mortally wounded during the Civil War by friendly fire.

During the more recent Gulf War campaign, 165 Americans were killed by friendly fire, according to the Defense Department. That is about 45 percent of all casualties suffered in the Gulf War.