The private soldiers were volunteers who were drawn from lower ranks of Victorian society. The available evidence shows that the bulk of private soldiers in the 53rd Foot were recruited from Ireland. A glance at the surnames in the attached database makes this clear. As Captain Oliver J Jones RN (who was attached to the 53rd Foot in a remarkably unofficial capacity for 5 months whilst taking a years’ leave from the Royal Navy) describes in his memoirs ‘A Winter Campaign in India 1857-1858’, the 53rd Foot was a “Catholic regiment”. - https://www.soldiersofshropshire.co.uk/wp-content/uploads/2021/11/53rd-in-Indian-mutiny.pdf
Only cursory, non-specific mentions of atrocities on 'both sides' in that doc, produced for the Soldiers of Shropshire Museum. Check out Newsinger for the full story if so inclined: https://erenow.net/modern/blood-never-dried-peoples-history-british-empire/5.php
Anyway, enough of this rabbithole!