Wow, where is this?
We have had to practice lockdown twice at our elementary school this last school year. The first times since the procedure was implemented in 2001. Once was for the immigration march the high schoolers did. They took a track right by our school, and the officials were just being cautious. But the other time was for shots fired. It actually turned out to be a transformer blowing, but it was scary for sure!
Do they know if it was a real bomb (one that could actually do damage) for sure? Or just that the bomb squad came (because they'll come if there's any suspicion of a bomb, even if it isn't one).