Wacky car alarm on my 2000 Honda Accord


So for the last few months my Honda Accord has been giving me problems with the alarm/anti-theft system. A few months ago I took it to a shop for some repairs, and left it overnight, and they said the alarm stopped working after a fire engine passed by. Then a week later I took it to my regular mechanic, and the alarm magically started working again. Now a few months later, it stopped working again, and now when I close all 4 doors, the alarm will go off. Sometimes the alarm even goes off if one of the doors is left open. This is becoming a pain in the ass especially when it goes off at 2AM, and is also embarrassing. I was life-guarding yesterday, and my alarm went off, and they made an announcement on the PA while I was guarding. How do I fix this?