DENVER >> Tribal members marked the 150th anniversary of the one of the American history’s worst massacres Wednesday by paying tribute at an old Denver cemetery to two U.S. Army officers who refused to participate in it.

On Nov. 29, 1864, Capt. Silas Soule and Lt. Joseph Cramer declined orders to open fire on an encampment of Cheyenne and Arapahoe men, women and children, in southeast Colorado.

About 200 people were killed in a dry riverbed that cold morning in what became known as the Sand Creek massacre.

On Wednesday, about 70 tribal members took part in a sunrise blessing at Riverside Cemetery before completing an annual healing run to the state Capitol, where Gov. John Hickenlooper apologized on behalf of the state for the massacre.

Some descendants of Sand Creek survivors credit Soule and Cramer with preventing even more bloodshed.

“It’s quite possible I wouldn’t be here if there was a prolonged attack of all the regiments,” said Otto Braided Hair, a Northern Cheyenne from near Lame Deer, Montana, whose great-grandparents survived the massacre.

In 1999, Braided Hair helped start the annual healing run that begins at the massacre site in Eads, about 180 miles southeast of Denver.

Cramer and Soule’s courage in speaking out against their commander helped the nation finally come to terms with what happened at Sand Creek.

Both came to Colorado seeking gold and enlisted in the army to fight in the Civil War. They likely fought under Col. John Chivington, who would lead the Sand Creek raid, in a battle that helped turn back an attempted Confederate incursion into Colorado’s gold country.

Both also attended peace conferences with the Arapaho and Cheyenne earlier in 1864, and they witnessed U.S. military commanders assuring chiefs they would be kept safe.

Those peace conferences occurred amid high tensions among settlers and tribes.

In June of that year, a settler family — Nathan and Ellen Hungate and their two young daughters — were killed on a ranch about 25 miles from Denver. Many blamed the Cheyenne and Arapaho for their deaths. Their bodies were brought to Denver and displayed on a main street.

A month before that, Cheyenne Chief Lean Bear, carrying a peace medal given to him by President Abraham Lincoln, was killed by the 1st Colorado Cavalry as he approached the troops, a slaying described by some as made in cold blood.

With tension on all sides, Chivington, a Civil War hero and Methodist minister, led troops from Denver to the outskirts of the camp of about 700 Arapaho and Cheyenne. The Indians believed they were safe after making peace with the commander of nearby Fort Lyon. They even flew a U.S. flag at the camp.

The soldiers opened fire, and some later brought victims’ body parts back to Denver. Chivington originally was hailed as a hero.

Cramer and Soule were part of Chivington’s forces but refused to order their own units to open fire. They later reported what happened, prompting a federal investigation that ultimately contributed to the resignation of territorial Gov. John Evans for failing to work for peace with tribes.

Soule’s criticism also apparently cost him his life. Less than three months after testifying in Washington against Chivington, he was fatally shot in downtown Denver. Two fellow soldiers were accused of killing him but were never brought to justice.

A lost letter from Soule to another officer about the massacre was found in 2000. It was read at a congressional hearing that eventually led to the creation of the Sand Creek Massacre National Historic Site in 2007.