AITAH for getting a store to enforce its 'one per customer' rule?

Thought I'd let Reddit decide this one...

I'm currently in Queensland, Australia, where there's a cyclone (aka typhoon/hurricane) has hit. Power has been out for 300,000 people now in many areas, including mine, for over 18 hours.

I've got medicine that needs to be kept refrigerated, so I drove 30mins through crazy weather to a convenience store that still has power, to get a bag of ice to keep them from spoiling. Right as I arrived, I saw a guy taking the last two bags of ice from the freezer, despite there being a LIMIT ONE PER CUSTOMER sign on the glass. 100% can't miss it.

I pointed it out to him and explained that I needed a bag for my meds and he said that he has a lot of frozen food that would go off if he didn't have enough ice. I said that the rules were there for a reason and that my meds were important to me, and he ignored me and walked off. I followed him to the checkout and told the cashier that he was breaking the rules and she sided with me and made him give me the second bag. He then sat out the front of the store and death stared me as I walked past, which I thought was ridiculous.

Am I in the wrong or were my actions justified? We are going through a natural disaster right now, and I had no idea where else to get ice from, but I also felt a bit uncomfortable telling the cashier. It's not something I'd usually do, but my meds are super important for my health.

Thoughts?