Their "republic" is a joke. They're a bunch of tyrants led by an even greater tyrant, that idiot Kimball. They think they have the right to annex every inch of dirt in the West and force their system on every man, woman, and child.
Samuel Cooke is the founder and former leader of the Powder Gangers. He was sent to the NCR Correctional Facility after waging a one-man campaign of mayhem against the NCR, blowing up supply caravans along the I-15. After leading the convicts in a successful uprising to take over NCRCF, Cooke left with a group of followers and went north, leaving Eddie as the Powder Ganger leader. Since then, Cooke and his personal gang of convicts reside in Vault 19, plotting to use the sulfur deposits underneath the vault to create explosives for a small-scale war against the NCR.
In contrast to Eddie and the Powder Gangers, whose reasons for hating the NCR are largely the normal antipathy of criminals toward the standing government, Cooke is described as having a revolutionary zeal, hating the NCR with an ideological passion. When asked why he hates the NCR so much, Cooke states that he hates how they feel they can just walk in and take whatever they want from the independent people of the Wasteland.
Killing Samuel Cooke will automatically turn all the Vault 19 convicts hostile, even if the kill is made stealthily with a silenced weapon or a planted explosive.
The convicts and Cooke may be hostile if you have a vilified reputation with the Powder Gangers, or if you have killed Papa Khan. However, this is usually not true and may be a bug.
Cooke's time as a prisoner was mentioned on the Warden's Terminal in the NCR Correctional Facility. He is said to be 'a model prisoner' and 'quite popular among the younger prisoners'. The warden says he is suspicious of Cooke, and would 'have him watched every second of every day'.