Three other convicts were involved in the main plan, Marvin Hubbard, Joseph Cretzer and Clarence Carnes.

He was moved to Alcatraz Federal Penitentiary in 1938 from Atlanta and was soon given the job of cell-house orderly, which gave him a relative amount of freedom of movement around the main cellblock.

He made a number of escape attempts and by 1946, when he was transferred to Alcatraz, had accumulated both a life sentence and 99 years for kidnapping.

Coy, as a cellhouse orderly, had over the years spotted a flaw in the bars protecting the gun gallery.

Coy kept the Springfield rifle in the gallery and lowered an M1911 pistol, keys, a number of clubs and gas grenades to his accomplices.

[3] Continuing along the gun gallery, Coy entered D Block, which was separated from the main cellhouse by a concrete wall and was used for prisoners kept in isolation.

The plan was to use the hostage officers as cover as the prisoners made their way to the dock, then San Francisco and freedom.

Miller had held on to the yard door key (against regulations), so that he could let out kitchen staff without having to disturb the gallery officer at lunch.

Associate warden Ed Miller went to the cellhouse to investigate, armed with a gas billy club.

Their plan having failed, Shockley and Thompson urged Cretzer, who had one of the guns, to kill the hostages in case they testified against them.

Carnes, Shockley, and Thompson returned to their cells, but Coy, Hubbard, and Cretzer decided they were not going to surrender.

Warden James A. Johnston asked for federal troops from nearby Naval Station Treasure Island to help deal with the situation.

There was a long-standing rule at Alcatraz that no guns were allowed in the cellhouse, and the prison officials did not want more officers injured or killed.

They eventually figured out that the rebellious prisoners were confined to the main cellhouse and ceased their attack until further tactics were worked out.

They drilled holes in the prison roof and dropped grenades into areas where they believed the convicts were located, to force them into a utility corridor where they could be cornered.

The following morning, squads of armed officers periodically rushed into the cellhouse, firing repeatedly into the narrow corridor.

Before the escape attempt, Hubbard had petitioned for a writ of habeas corpus on the grounds that his confession had been beaten out of him; he had produced hospital records to back up his claims.

The case was dismissed on a motion filed by prosecutor Joseph Karesh, who is quoted as saying that had it gone through, Hubbard would have had "a fair chance" of being released.

[3] Miran Thompson and Sam Shockley were executed simultaneously in the gas chamber at San Quentin on December 3, 1948, for their roles in the Battle of Alcatraz.

Carnes was spared from execution after numerous officers taken hostage testified that he'd refrained from carrying out orders to kill them.