One of the loan sharks, Leo Ruggeri, is located in the Butcher Block shop. There are two guards and one sentry in the back door. Nevertheless, it should be easy to take them out especially you trigger a shootout with the nearby beatdown crew since it will draw the attention of the guards without spooking the loan shark.
Trash Protected Liquor Stores
This objective becomes available after successfully interrogating one of the loan sharks. There are three protected liquor stores you can infiltrate. You need to steal the cash and/or destroy the booze to deal damage. You can sneak from the liquor store's back door. The “protectors” of these establishments are just chilling inside a car in front of the store so you can just walk to them and kill them all before they disembark. Be careful since witnesses will tend to call the cops when the shootout starts so make sure to finish up quickly and take care of any witnesses and / or use the Police Dispatcher associate.