A shocking sense of loss. An almost-frantic search for explanations. Lingering questions about how it could have happened. A desperate search for ways to prevent it from happing again. Deep-seated anger.All have been part of the nation's emotional reaction in the days since a troubled 20-year-old forced his way into Sandy Hook Elementary School in Newtown, Conn., on Friday and brutally murdered 20 children, 6- and 7-year-old innocents, and six adults. His just-as-brutal killing of his mother earlier that day added to the tragedy.As the gruesome details trickled out from the ongoing police investigation, the national conversation quickly focused, justifiably, on further efforts at gun control, school safety and ways to help people with mental health conditions before they reach a tragic breaking point.These issues have been examined before in the wake of other mass killings: Colorado's Columbine High School massacre in 1999; Fort Worth's Wedgwood Baptist Church shootings that same year; the Virginia Tech killings in 2007; the slaying of 13 soldiers at Fort Hood in 2009; a Tucson shooter's rampage against then-Rep. Gabrielle Giffords and others in 2011; and the mass murders in an Aurora, Colo., movie theater and a Wisconsin Sikh temple this year.The Connecticut killer's actions Friday gave mocking evidence that it's worthwhile to have those discussions again. The tiny bodies of 20 first-graders make reconsideration essential and, this time, require results that will forestall additions to the list.The gun control nerve has been struck with lasting pain this time. President Barack Obama mentioned it, however obliquely ("I will use whatever power this office holds....") during an interfaith vigil Sunday in Newtown.Sens. Joe Manchin of West Virginia and Mark Warner of Virginia, both pro-gun Democrats, have called for a re-thinking of gun control."You know, enough is enough," Warner told CBS station WTVR/Channel 6 in Richmond, Va. Neither Warner nor Manchin offered specific legislation.There are plenty of gun control issues to be addressed again, from assault rifles to multi-round ammunition magazines to bullets designed for maximum tissue damage, all used by the Newtown killer. It's time to see whether old arguments ("If guns are banned, only bad guys will have guns") really hold up. The National Rifle Association's views are not sacred.The right to bear arms is backed by the Second Amendment, but that needn't rule out rational steps to curb deadly weapons and ammunition in order to help break the terrible string of mass killings.School safety also demands re-examination. The odds of any individual school being hit by a deranged killer are small, but odds are not what you want to hear when it's your child in that school. We remodel schools to minimize the risk from fire or tornado, also statistically rare.The answer is not, as some have suggested, arming teachers. Our nation should have better answers than fighting guns with more guns. The answer is to devise ways to stop intruders before they enter classroom areas -- better ways than what was in place at Sandy Hook Elementary.Mental health professionals have much they can teach us about people who commit these violent acts. We all have an obligation to learn and to find ways to better support their efforts.Facing the horror of Friday's shootings in Newtown made for a difficult weekend. The goal now must be to make this not just another aftermath of another mass killing.