An inmate involved in a bloody 1971 San Quentin escape attempt that left six dead has been killed by a fellow prisoner, corrections officials said Wednesday.

The slaying of Hugo Pinell, 71, triggered a riot Wednesday that grew to involve about 70 inmates at a maximum security prison east of Sacramento, said California Department of Corrections and Rehabilitation spokeswoman Dana Simas.

"He was definitely the target," Simas said. She would not give more information about the alleged attacker for his own protection.

Once Pinell was attacked in a California State Prison, Sacramento, exercise yard by his fellow inmate, "everyone else joined in," Simas said, including members of multiple prison gangs.

Eleven other inmates were taken to an outside hospital to be treated for stab wounds, while other injured inmates were treated at the prison. No employees were harmed. Guards fired three shots and used pepper spray to break up the brawl.

Officials initially said about 100 inmates were involved and five hospitalized.

Forty-four years ago, Pinell helped slit the throats of San Quentin prison guards during an escape attempt that led to the deaths of three guards, two inmate trustees and escape ringleader George Jackson, who was fatally shot as he ran toward an outside prison wall, according to Associated Press stories.

Jackson was a Black Panther leader, founder of the Black Guerrilla Family prison gang, and author of the 1970 book "Soledad Brother," written after he and other inmates were accused in the slaying of a Soledad prison guard in January 1970.

Guards testified that Jackson started the escape attempt when he pulled a smuggled 9-mm pistol from under his six-inch-high Afro hairdo and fatally shot two correctional officers.

Correctional Officer Urbano Rubiaco Jr. survived to later testify that Pinell used a knife made of razor blades embedded in a toothbrush handle to slash Rubiaco's neck.

"He said 'I love you pigs' and then he cut my throat," Rubiaco said. He was one of two guards taken hostage by 25 inmates who were released from their cells during the escape attempt.

Correctional Sgt. Frank McCray testified that he and other guards were blindfolded, bound and piled into a cell, where McCray said his throat also was cut while other guards were shot and strangled.

A jury eventually acquitted Jackson's lawyer, Stephen Bingham, a grandson of former Connecticut Gov. Hiram Bingham, of smuggling in the gun.

Pinell and five other inmates became known as the San Quentin Six. Only one, 61-year-old William "Willie" Tate, remains in prison, at the Correctional Training Facility in Soledad.

The others were freed years ago: Fleeta Drumgo and Luis Talamantez in 1976, Johnny Larry Spain in 1991 and David Johnson in 1993.

Pinell was initially sent to prison in 1965 to serve a life sentence for a San Francisco rape. He was given a second life sentence for killing Correctional Officer R.J. McCarthey in 1971 at the Soledad prison.

He was given a third life sentence, all with the possibility of parole, for the San Quentin escape attempt after he was convicted of assaulting two correctional officers.

Prisoners remained locked in their cells as officers investigated Wednesday's disturbance.

The prison commonly called New Folsom houses more than 2,300 maximum-security inmates in Folsom, a suburb about 25 miles east of the state capital.