Question: The Centralia Massacre was committed by which pro-Confederate guerrilla leader?

full_context: Document 1: Lawrence massacre: The Lawrence massacre, also known as Quantrill's raid, was an attack during the American Civil War (1861-1865) by the Quantrill's Raiders, a Confederate guerilla group led by William Quantrill, on the Unionist town of Lawrence, Kansas.
Document 2: Cole Younger: Thomas Coleman "Cole" Younger (January 15, 1844 – March 21, 1916) was an American Confederate guerrilla during the American Civil War and later an outlaw leader with the James–Younger Gang. He was the eldest brother of Jim, John and Bob Younger, who were also members of the gang.
Document 3: Marais des Cygnes massacre: The Marais des Cygnes massacre ( , , or ) is considered the last significant act of violence in Bleeding Kansas prior to the outbreak of the American Civil War. On May 19, 1858, approximately 30 men led by Charles Hamilton, a Georgian native and proslavery leader, crossed into the Kansas Territory from Missouri. They arrived at Trading Post, Kansas, in the morning and then headed back to Missouri. Along the way they captured 11 Free-Staters, none of whom were armed and, it is said, none of whom had participated in the ongoing violence. Most of the men knew Hamilton and apparently did not realize he meant them harm. These prisoners were led into a defile, where Hamilton ordered the men to shoot. He even shot and fired the first bullet himself. Five men were killed.
Document 4: William T. Anderson: William T. Anderson (1840 – October 26, 1864)—known as "Bloody Bill" Anderson—was one of the deadliest and most brutal pro-Confederate guerrilla leaders in the American Civil War. Anderson led a band that targeted Union loyalists and Federal soldiers in Missouri and Kansas.
Document 5: Jayhawker: Jayhawkers is a term that came to prominence just before the American Civil War in Bleeding Kansas, where it was adopted by militant bands affiliated with the free-state cause. These bands, known as "Jayhawkers", were guerrilla fighters who often clashed with pro-slavery groups from Missouri known at the time as "Border Ruffians". After the Civil War, the word "Jayhawker" became synonymous with the people of Kansas. Today a modified version of the term, Jayhawk, is used as a nickname for a native-born Kansan, but more typically for a student, fan, or alumnus of the University of Kansas.
Document 6: Skirmish at Albany, Missouri: The Skirmish at Albany, Missouri was a battle that was fought between the Union army and the Quantrill's Raiders in Gentey County, Missouri on October 26, 1864. The battle resulted a Union victory and the notorious Quantrill Raider Member William T. Anderson also known as Bloody Bill, was killed at this battle.
Document 7: John Brown (abolitionist): John Brown (May 9, 1800 – December 2, 1859) was an American abolitionist who believed and advocated that armed insurrection was the only way to overthrow the institution of slavery in the United States. Brown first gained attention when he led small groups of volunteers during the Bleeding Kansas crisis of 1856. Dissatisfied with the pacifism of the organized abolitionist movement, he said, "These men are all talk. What we need is action—action!" During the Kansas campaign, Brown commanded forces at the Battle of Black Jack and the Battle of Osawatomie. He and his supporters killed five supporters of slavery in the Pottawatomie massacre of May 1856 in response to the sacking of Lawrence by pro-slavery forces.
Document 8: Centralia massacre (Washington): The Centralia Massacre, also known as the Armistice Day Riot, was a violent and bloody incident that occurred in Centralia, Washington, on November 11, 1919, during a parade celebrating the first anniversary of Armistice Day. This conflict between the American Legion and workers who were members of the Industrial Workers of the World (IWW or "Wobblies") resulted in six deaths, additional wounded, multiple prison terms, and an ongoing and especially bitter dispute over the motivations and events that precipitated the massacre. It was the culmination of years of bad blood between members of the local Legion and members of the IWW. Both Centralia and the neighboring town of Chehalis had a large number of World War I veterans, with robust chapters of the Legion, as well as a large number of IWW members, some also war veterans.
Document 9: Mount Oread Civil War posts: Lawrence, Kansas was not well defended in the early part of the Civil War. That ended with William Quantrill's devastating guerrilla raid August 21, 1863. By early 1864 Union soldiers were permanently camped on the top and slopes of Mount Oread, then to Lawrence's southwest. It seems the camp was originally named Camp Ewing, after Brig. Gen. Thomas Ewing.
Document 10: William Quantrill: William Clarke Quantrill (July 31, 1837 – June 6, 1865) was a Confederate leader during the American Civil War.
Document 11: Samuel P. Cox: Samuel P. Cox (December 16, 1828 – August 21, 1913) was a businessman and farmer who is best remembered as the commander of the Union troops that killed "Bloody Bill" Anderson in the Battle of Albany in the American Civil War.
Document 12: Centralia Massacre (Missouri): The Centralia Massacre was an incident during the American Civil War in which twenty-four unarmed Union soldiers were captured and executed at Centralia, Missouri on September 27, 1864 by the pro-Confederate guerrilla leader William T. Anderson. Future outlaw Jesse James was among the guerrillas.
Document 13: Archie Clement: Archie Clement (January 1, 1846 – December 13, 1866), also known as "Little Arch", was a pro-Confederate guerrilla leader during the American Civil War, known for his brutality towards Union soldiers and pro-Union civilians in the state of Missouri.
Document 14: Jesse James: Jesse Woodson James (September 5, 1847April 3, 1882) was an American outlaw, bank and train robber, guerrilla, and leader of the James–Younger Gang. Raised in the "Little Dixie" area of western Missouri, James and his family maintained strong Southern sympathies. He and his brother Frank James joined pro-Confederate guerrillas known as "bushwhackers" operating in Missouri and Kansas during the American Civil War. As followers of William Quantrill and "Bloody Bill" Anderson, they were accused of participating in atrocities against Union soldiers and civilian abolitionists, including the Centralia Massacre in 1864.
Document 15: Quantrill's Raiders: Quantrill's Raiders were the best-known of the pro-Confederate partisan rangers ("bushwhackers") who fought in the American Civil War. Their leader was William Quantrill and they included Jesse James and his brother Frank.
ground_truth: William T. Anderson