How do I shut this alarm off?

In the "store within a store" (2 aisles that have been walled off for degergent, meds, razors, etc) the alarm for the back door randomly went off and we can't figure out how to turn it off. We can't figure how to use the key for the door reset. I'm here for another 2 hours and this thing is gonna be the death of me. Please help 💙