The memory of Oct. 1, 2004, will be forever etched in the mind of Army Sgt. Larry Cannon.

He had to pull a dead baby from the arms of a screaming mother who had been shot several times in Samarra, Iraq, and needed emergency medical care.

"I took the baby and set it on the sidewalk — I didn't know what else to do," Cannon said Monday, speaking to hundreds who gathered at Salt Lake City's Washington Square in protest of the war in Iraq on the fourth anniversary of the invasion.

"Another woman no older than me ... was shot many times, too," Cannon said. "She died in my arms a few minutes later, as we were trying to rush her out of town to get help."

That, Cannon said, was the worst day of his life.

It had happened during a break in fighting, said Cannon, now a University of Utah student. He served in Iraq from January 2004 to March 2005.

On that October day, Cannon had just received a call about a white sedan that might be a car bomb. He relayed the information to his fellow soldiers. Then, he heard their shooting. When he arrived at the scene, he found a carful of innocent victims, including the mother and baby.

It turns out, he said, that the suspected car bomb was simply a family trying to get out of the city before the battle resumed.

"People argue that terrible things happen in war. Believe me, I know," Cannon said. "What I don't know is why we have to learn this terrible lesson over and over again."

About 500 people marched from Pioneer Park to Washington Square, led by six men carrying a mock coffin draped in an American flag. Chants of "War no more" were heard as the protesters arrived for the rally organized by People for Peace and Justice.

Coinciding with rallies across the nation, the protesters used the four-year anniversary of the invasion to speak out against Bush's plan to send 21,500 additional U.S. troops to Iraq and call for an end to the war.

Salt Lake City Mayor Rocky Anderson repeated his call for the impeachment of President Bush as the only remedy for a "blight on our nation's honor."

While Anderson was greeted with enthusiastic cheers Monday, the mayor's activism against the war has been controversial. His critics say he has overstepped his role as a mayor.

Anderson also spoke at an anti-war rally in Washington, D.C., this past weekend. He sparked controversy last year by speaking against the war while Bush was in town for a Veterans of Foreign Wars convention.

Later Monday, Anderson echoed his call for impeachment when interviewed by Wolf Blitzer on CNN's "The Situation Room."