Green’s Dictionary of Slang

(US black gang) to perform an armed robbery, usu. of neighborhood stores or individuals.

2016		F. Stuart ‘Dispatches from the Rap Wars’ in chicagomag.com 🌐 one way shooters make money is by “staining,” or stealing from people or stores in nearby neighborhoods.
2018-20		T. Thorne (ed.) ‘Drill Slang Glossary’ at Forensic Linguistic Databank 🌐 Stain - rob.