How do I talk about "terror days" with my first-grader?

My tactic was to go about the day and handle questions as they came. I had to take my 4-year-old to a doctor’s appointment, and when the local National Public Radio affiliate started talking about the schools being shut down, I quickly changed the channel. My older son began to say, “Hey, they’re talking about my school…” but then he changed the topic. As little as he knew, he’d picked up enough to understand that something was wrong. He didn’t want to scare his younger brother.

Of course, the TV news was on — loud — in the doctor’s waiting room. Then we got an email from my younger son’s preschool. Because of the terror threat, the Los Angeles Police Department recommended that all schools — public and private — close for the day, and the preschool would comply. The Christmas show, scheduled for the night, would be postponed.

There was no avoiding it anymore.

And yet, I knew so little. Was this a real threat? A hoax? Does it matter?