Most popular Jack the Ripper theories from ripperologists just blame immigrants, but personally I think it was British empire soldiers...guys who'd just come back from committing massacres in Africa and Asia and figured, why stop now?
The British army committed tons of mutilations during the massacres they committed in colonial times. Removing breasts and mutilating uteruses has been recorded before. In India, in Kenya etcetera.
It's silly to think Jack the Ripper was just some random blue-collar worker from Poland instead of a soldier who probably just came back from the Xhosa Wars, for example.
And Xhosa Wars happened about a decade before the first Whitechapel murder.