Silas Soule Silas Stillman Soule ( July 26 , 1838 – April 23 , 1865 ) was a Massachusetts abolitionist , Kansas Territory Jayhawker anti - slavery militant , and later an officer in the Colorado infantry and cavalry during the American Civil War . Captain Soule was in command of Company D , 1st Colorado Cavalry , which was present at the Sand Creek Massacre on November 29 , 1864 . He refused an order of his commander , Colonel John Chivington , to join an attack a peaceful encampment of members of the Southern Cheyenne and Arapaho tribes . Soule later testified against Chivington for the atrocities committed at Sand Creek , and was assassinated on a street in Denver soon afterward . The shooting was believed to have been an act of premeditated murder by Chivington loyalists as revenge for his testifying . Early life and " Bleeding Kansas " . Silas Soule was born into a family of abolitionists in Bath , Maine . He was raised in Maine and Massachusetts and , in 1854 , his family became part of the newly formed New England Emigrant Aid Company , an organization whose goal was to help settle the Kansas Territory and bring it into the Union as a free state . His father and brother arrived in Kansas , near Lawrence , in November 1854 . Silas , his mother and two sisters came the following summer . Border war . Shortly after the family ' s arrival at Coal Creek , a few miles south of Lawrence near present day Vinland , Amasa Soule , Silas ' s father , established his household as a stop on the Underground Railroad . At the young age of 17 , Silas was escorting slaves , escapees from Missouri , north to freedom . Silas ' s sister , Anne Julia Soule Prentiss , tells of her family ' s early experience in Maine , Massachusetts and Kansas in a 1929 interview . " Our house was on the ' Underground Railway ' . John Brown was often there . . . My Brother , Silas , and Brown were close friends . Silas went out on many a foray with him . I recall well when Brown came to our cabin one night with thirteen slaves , men , women and children . He had run them away from Missouri . Brown left them with us . Father would always take in all the Negroes he could . Silas took the whole thirteen from our home eight miles to Mr . Grover ' s stone barn . . . " During these pre - war years pro - slavery forces from Missouri and abolitionist forces from Kansas were engaged in open warfare . The fight was whether Kansas would be admitted to the Union as a slave or as a free state . This conflict , often called Bleeding Kansas , enhanced the reputation of Silas Soule as a brave and resourceful fighter . In July , 1859 , Soule was part of an action on the Missouri Border . Twenty pro - slavery men had crossed into Kansas to look for escaped slaves . They ambushed a party led by Dr . John Doy , a physician in Lawrence , escorting 13 former slaves , 8 men , three women and two children toward safety in Iowa . The men from Missouri arrested Dr . Doy and sold the former slaves . Doy was soon tried and convicted in Missouri for abducting slaves and sentenced to 5 years in the penitentiary . Soule and a group of other men from Lawrence decided to free Doy . Soule was sent into the jail house in St . Joseph where Doy was being held . Soule convinced the jailkeeper that he had a message from Doy ' s wife . The note , in fact , read " Tonight , at twelve o ' clock . " Later that night , they overpowered the jailer , freed Doy , and led him across the Missouri back to Kansas . When they reached Lawrence , they had their photo taken . ( This photo of " The Immortal Ten , " now held by the Kansas State Historical Society , is widely circulated . ) His skills at prison escapes came into use once again when John Brown , a friend of the Soule family , was captured after his raid on Harper ' s Ferry . Brown had decided to become a martyr for the abolitionist cause and allowed himself to be hanged , hoping his death would help bring on a war between north and south , and frustrating rescue attempts . Thomas Wentworth Higginson put together a rescue attempt of two of Brown ' s men , Albert Hazlett and Aaron Stevens , during which Silas posed as a drunken Irishman and got himself arrested . Put into the Charlestown jail , he charmed the jailor and contacted the two men , who also refused to be sprung from the jail . Afterwards , Silas traveled to Boston , where he hobnobbed with various abolitionists and befriended the poet Walt Whitman . Military service and the Sand Creek Massacre . In May , 1860 Silas , along with his brother William L . G . Soule , and his cousin , Sam Glass , went to the gold fields in Colorado . " When I arrived here I found a party waiting for me to go to pikes peak . My Brother and cousin were in the gang going with a quartz machine belonging to Solomon and Parker of Lawrence and there was no way but I must go . " Soule dug for gold and worked in a blacksmith shop , and then in December , 1861 , he enlisted in Company K , 1st Colorado Volunteers . He made his way up the ranks , and in November 1864 , was named commander of Company D , 1st Colorado Cavalry . On November 29 , 1864 , Captain Soule and his company were with the regiment at Sand Creek , Colorado . Col . John Chivington ordered the cavalry to attack the Cheyenne encampment . Soule saw that the Cheyenne were flying the U . S . flag as a sign of peace , and , when told to attack , ordered his men to hold their fire and stay put . Most of Chivington ' s other forces , however , immediately attacked . The resulting action is now known as the Sand Creek Massacre , one of the biggest mass slaughters in U . S . history . Chivington was furious over Soule ' s refusal to attack the camp and branded him a coward . Soule ' s men came to his defense , saying that Soule was indeed very courageous in refusing Chivington ' s order . Testimony and death . The massacre sparked outrage and shock around the country . The United States Army began an investigation into the " battle , " and Soule formally testified against Chivington in a court of inquiry . On April 23 , 1865 , a U . S . soldier named Charles W . Squier shot Soule in the head near his Denver home , killing him . It was thought at the time by many that Squier was hired by men loyal to Chivington to kill Soule . One of Soule ' s friends , First Lieutenant James Cannon , tracked Squier down in New Mexico and brought him back to Denver to stand trial . Squier escaped and Cannon was poisoned . Squier was never again captured and escaped punishment . Soule ' s testimony against Chivington and about the massacre at Sand Creek led , in part , the United States Congress to refuse the Army ' s request for thousands of men for a general war against the Native Americans of the Plains States . Memorial . A memorial plaque was placed on a building at the northwest corner of Fifteenth and Arapaho Streets in Denver , marking the spot was Silas Soule was assassinated . The plaque reads : “ Silas S . Soule . At this location on April 23 , 1865 , assassins shot and killed 1st Colorado Cavalry officer Capt . Silas S . Soule . During the infamous Sand Creek Massacre of November 29 , 1864 , Soule had disobeyed orders by refusing to fire on Chief Black Kettle ’ s peaceful Cheyenne and Arapaho village . Later , at army hearings , Soule testified against his commander , Col . John M . Chivington , detailing the atrocities committed by the troops at Sand Creek . His murderers were never brought to justice . ”