Legal Question in Civil Litigation in Connecticut

It would depend on a lot of factors. Was the money loaned to the store owner personally, or was it loaned to the store itself? Was the loan documented in writing? Were any guarantees signed? Does your operating agreement address responsibility for debts?

If the money was loaned to the owner personally, for that owner's personal use, a co-owner would not be responsible for his partner's personal debts. If the money was loaned to the store's entity, there is a good chance both partners will be jointly liable. But there is no clear answer without a complete description of the transaction.