Question: The San Quentin Six were six inmates at San Quentin State Prison in the U.S. state of California, they were accused of participating in an escape attempt, on which date, that left six people dead, including George Jackson, a co-founder of the Black Guerrilla Family?

Context paragraphs:
Squires of San Quentin: Squires of San Quentin is a 1978 American short documentary film produced by J. Gary Mitchell.  It was nominated for an Academy Award for Best Documentary Short.  The film was shot in San Quentin State Prison and depicts "The Squires", inmates who attempt to convince troubled children to avoid criminal behavior.

George Jackson (activist): George Lester Jackson (September 23, 1941 – August 21, 1971) was an African-American activist and author.  While serving a sentence for armed robbery in 1961, Jackson became involved in revolutionary activity and co-founded the Maoist-Marxist Black Guerrilla Family.  In 1970, he was charged, along with two other Soledad Brothers, with the murder of prison guard John Vincent Mills in the aftermath of a prison fight.  The same year, he published "Soledad Brother: The Prison Letters of George Jackson", a combination of autobiography and manifesto addressed to a black American audience.  The book would become a best-seller and earn Jackson personal fame.  In 1971, Jackson took several guards and two inmates hostage in a bid to escape from San Quentin Prison.  However, the incident ended with Jackson being shot and killed by a guard, in addition to the deaths of 5 hostages.

Gary W. Thomas: Gary W. Thomas (March 19, 1938 – April 3, 2017) was a Marin County, California prosecutor and Superior Court judge.  Thomas was primarily known for his role in the Marin County Civic Center shootout in which he was taken hostage in a courtroom, along with Judge Harold Haley and three female jurors, by Jonathan Jackson and three inmates from San Quentin State Prison in what is widely speculated to be a failed attempt to free his brother, George Jackson, and the other two Soledad Brothers.  Haley, Jonathan Jackson, and two of the inmates were killed during the escape attempt, and Thomas was paralyzed from the waist down.

Stephen Bingham: Stephen Mitchell Bingham (born April 23, 1942) is an American legal services and civil rights attorney who was tried and acquitted in 1986 for his alleged role in Black Panther George Jackson's attempted escape fifteen years earlier from San Quentin State Prison in Marin County, California, in 1971.

Black Guerrilla Family: The Black Guerilla Family, or BGF (also known as the Black Family or the Black Vanguard) is an African-American prison and street gang founded in 1966 by George Jackson and W.L. Nolen while they were incarcerated at San Quentin State Prison in Marin County, California.

Attica Prison riot: The Attica Prison riot, also known as the Attica Prison rebellion or Attica Prison uprising, occurred at the Attica Correctional Facility in Attica, New York, United States in 1971.  Based upon prisoners' demands for better living conditions and political rights, the riot was one of the most well-known and significant uprisings of the Prisoners' Rights Movement.  On September 9, 1971, two weeks after the killing of George Jackson at San Quentin State Prison, about 1,000 of the Attica prison's approximately 2,200 inmates rioted and took control of the prison, taking 42 staff hostage.

San Quentin State Prison: San Quentin State Prison (SQ) is a California Department of Corrections and Rehabilitation state prison for men, located north of San Francisco in the unincorporated town of San Quentin in Marin County.

San Quentin Six: The San Quentin Six were six inmates at San Quentin State Prison in the U.S. state of California (Hugo Pinell, Willie Tate, Johnny Larry Spain, David Johnson, Fleeta Drumgo and Luis Talamantez), who were accused of participating in an August 21, 1971 escape attempt that left six people dead, including George Jackson, a co-founder of the Black Guerrilla Family.

George Jackson Brigade: The George Jackson Brigade, was a revolutionary group based in Seattle, Washington, which was named after George Jackson, a dissident prisoner and Black Panther member shot and killed during an alleged escape attempt at San Quentin Prison in 1971.

California Reentry Program: The California Reentry Program (CRP) is a non-profit organization with the mission of helping California prisoners successfully reenter society.  It has operated in San Quentin State Prison since 2003 when Allyson West, an algebra teacher at San Quentin at the time, helped one inmate with the reentry process and realized the importance of reentry work and the lack of ability or interest of the state to reduce recidivism.  Working with San Quentin and recruiting volunteers, West founded the California Reentry Program which has helped several thousand prisoners so far.  CRP's mission is to help all California prisoners, but due to lack of resources, it only operates in San Quentin.  CRP incorporated in 2007 and received non-profit status in 2008.  CRP has roughly 25 volunteers and helps about 150-200 clients per month.

Supporting paragraphs: San Quentin Six Black Guerrilla Family
Answer: August 21, 1971