Green’s Dictionary of Slang

(US) a swindler, a crooked gambler.

1859		Matsell Vocabulum 39: guerrillas This name is applied by gamblers to fellows who skin suckers when and where they can, who do not like the professional gamblers, but try to beat them, sometimes inform on them, and tell the suckers that they have been cheated.
1885		Harper’s Mag. Nov. 839/1: The guerrillas are a sub-class of the scalpers, few in number, and by making specialty of dealing in inactive stocks have formerly fixed the unsavory appellations of ‘Hell’s Kitchen’ and ‘Robber’s Roost’ upon certain localities of the floor [DA].