Nu York, New York: Reading, writing and violence?

In recent years we have read terrifying stories of Jewish schools being targeted by anti-Semitic terrorists. Jewish schools in France and Belgium, Holland and of course in Israel, as well as in other countries, have been struck by violence or by threats of violence. It is sickening and has spurred schools to take major precautions for safety.
In recent years we have also read terrifying stories of secular schools in various parts of the United States that have been rocked by violence. Shootings perpetrated by intruders as well as by students have been carried out. Sandy Hook Elementary School, Columbine High School and others have been seared into our minds.
In this kind of atmosphere, how would you react if you received the following text from your child:
 "My school is on lockdown."
What thoughts would go through your head? Is your child indeed in grave danger? Or is it less severe but still something to be concerned about?
On Wednesday, January 21st, I was working at home, editing a manuscript on my desktop computer. At 1:29PM I received this simple yet ominous text from my older daughter. I didn't freak out, but I was certainly concerned. Yet I also wanted to keep her calm. Here is part of our text-conversation:
Me: Stay calm. What class and room u in?
Jess: We're in science.
Me: I bet a kid cut out and guards r searching for her or him.
Jess: Someone says someone had a gun in the school. IDK (I don't know) if that's true.
Me: Don't worry.
Jess: Really. Do you know what's happening?
Me: I called the school no answer at switchboard do I call police precinct?
Jess: IDK. I hope it's nothing bad.
We exchanged more messages and I did call the Police Precinct, the 70th (Brooklyn and New York City overall have so many precincts). Someone there said that police had been dispatched to the school. I went over and found dozens of parents, a small TV news crew and a few photographers. The mood was apprehensive but not manic.
After a two-hour plus lockdown we found out that it was all a false alarm. Apparently a teacher saw three male students walking in a stairwell, carrying shop tools (the school has a Stage Crew and Theater Production classes). The teacher did not recognize the kids and thought they had knives, so the teacher called in the warning.
Of course, most of us breathed a major sigh of collective relief. At 5PM we received a phone call from the school principal, explaining what had transpired. In addition we received an email about the incident. Rumors still went around and at least one person I know called it a cover up, even though major news outlets debunked that and described the situation as a false alarm.
"An abundance of caution" was the phrase employed. Yes, indeed.
But while I am glad that my daughter's school is okay and everyone is safe (this school is my alma mater as well), I couldn't help but think about the American schools hit by violence, the European and Israeli schools also hit by violence. The Jewish schools as well as the secular schools. In this kind of environment, is it surprising that a teacher perceived this as a threat? Or did the teacher overreact?