A gunman shot and killed Virginia Tech university police officer Deriek Crouse on Thursday, sending a wave of fear across a campus still scarred by a 2007 rampage that left 33 people dead. State troopers with automatic weapons swarmed the school grounds as university officials set in motion lockdown procedures developed in the wake of the 2007 tragedy, only issuing the all-clear after the presumed gunman was found dead, an apparent suicide, in a nearby parking lot. What can we learn from this sad episode? Here, three lessons:

1. Society has lost its moral compass
The problem isn't that America has too many guns or lax campus security, says Tim Stanley at Britain's Telegraph. "Remove the specific conditions of the murders at Virginia Tech, like the weaponry used or the fact that they took place on American soil, and you have a spate of crimes that is indicative of ubiquitous moral failure." We don't know yet what motivated Thursday's shooter, but we do know that the 2007 gunman — 23-year-old Seung-Hui Cho — "was a sick man who had fallen through the cracks." Clearly, "we are not doing enough to love each other. We must do more."

2. Sadly, "pure evil" will always exist
"When we hear of such horrible tragedies like the Virginia Tech shootings," says Rabbi Shmuel Herzfeld in The Washington Post, we are reminded that "there will always be pure evil in our midst." We all "have a responsibility to forcefully fight against such evil." During the 2007 rampage, the shooter's evil was met with many acts of courage, such as that shown by Holocaust survivor Liviu Librescu, a 76-year-old professor who saved lives by throwing himself in front of his classroom door, taking bullets while telling his students to run to safety. The rest of us can fight back too, before evil strikes, "by spreading acts of goodness in the world."

3. But information can save lives
University officials faced intense criticism for their slow response in 2007 when disturbed English major Seung-Hui Cho went on his killing spree, says Mark Guarino in The Christian Science Monitor. In the "chaotic minutes" after Thursday's tragic shooting, the university was "forced to test" the emergency response procedures it has since developed. The system worked flawlessly, with students and teachers kept safe behind locked doors. A stream of tweets, text messages, emails, phone calls, classroom alerts, and sirens kept everyone on the 30,000-student campus well informed until, after four hours, they were told it was safe to come out.