Who pulled the fire alarm?

This is a shot of the school that I was enrolling at. All the kids were lined up outside the school because the fire alarm went off. I found out that this was only a test. I haven't done a fire drill in quite a long while. It went off when I was in the middle of presenting. The employee I was talking to flinched when it went off. I was just stunned because I didn't know what was going on. I parked my car across the street and when I came out of the building to leave, I found my car surrounded by fire engines. I couldn't leave until the crossing guard gave me some help.