Then, years later, I heard another person say we lost our innocence when Lyle Menendez went out and reloaded his guns. The Menendez boys’ murder of their parents in 1989 is still—I’m fairly certain—the most brutal in the annals of American family crimes. It wasn’t enough to riddle his mother with bullets. Lyle reloaded the gun and blew part of her head off.

If we had any innocence left, surely we lost more of it on April 20, 1999, when Eric Harris and Dylan Klebold opened fire on the students of Columbine High School, killing 13 and wounding 21 before turning their guns on themselves.

With the latest school shootings this week, the word “again” underscores how much we have lost in these violent times. On Friday, the principal of a school in rural Cazenovia, Wis., was apparently shot and killed by a former student. Just two days prior, 16-year-old Emily Keyes was killed in Bailey, Colo., by a madman that sexually assaulted several young women that he had taken hostage.

Schools, while perhaps not the sanctuaries that churches have historically been, were once considered fairly safe havens. When I was in school, our high crimes and misdemeanors consisted of smoking cigarettes in the bathroom and cutting class to go make out in a broom closet.

There is a whole generation of children who will never know a world before Columbine, who will always be at least peripherally aware that guns can find their way onto school grounds and massacres can happen, who will look at the loner in class, the troubled outsider, or the stranger who has wandered onto school property and wonder if this will be the day, if they will be the next news story or the next casualty.

There is no way to insulate children from a world that has become increasingly brutal. Kids who were born in 1999 are now 7 years old. They know about Columbine. They know about the shooting in Bailey. They know about the countless other school shootings and foiled plots by troubled teens of recent years. They may even know about the horrible 2004 hostage crisis in Beslan, Russia, where more than 300 died. They know there are no safe havens anymore.

But maybe there are safe havens in the memories of those of us who are old enough to remember a different world. Maybe the best we can do is make sure those memories stay alive and are implanted in children whose history is more war-torn than ours ever was. Because to lose those memories is to lose hope that we can someday re-create a world in which kids can go to school without fearing for their lives.

Maybe there is an ebb and flow to innocence, and it can return—what seems lost to us now can in time flow again. For all of us who do remember a time before the name Columbine ushered in horrible images, we have a responsibility to keep that time alive, if only in memory, so that memory can shape a more innocent future.