Intrusion alarm...intruder in the building...

On wednesday, Sierra (one of my co-workers) and I decided to stay a little late to work on a project together. We ran to the store to get a few things for our project and came back to her room at school to work. Luckily, one of the nice custodians was vacuuming Sierra's room and we were able to knock on the window so she could let us back in the building. We asked her what time they would be locking up and she said around 7 or 7:30. I told her to just let us know when we needed to leave. We had been sitting at a table just working away, I had stood up to go get a kleenex (gotta love cold season!) when all of the sudden the loud speaker comes on. Sierra and i both look at each other in confusion wondering who would be making an anouncement this late at night. Then all of a sudden a siren goes off and we here over the speaker "INTRUSION ALARM, INTRUDER IN THE BUILDING...INTRUSION ALARM, INTRUDER IN THE BUILDING...INTRUSION ALARM, INTRUDER IN THE BUILDING..." At first we were both a little freaked out, then we realilzed the intruders were US! Luckily I had Sue's (our principal) cell phone number in my phone. I called here and we got ahold of Brian (our head custodian) and we got it all worked out. The Alarm finally went off after about 5 minutes! It was quite the evening!