Addressing an auditorium of grieving parents, first responders and members of the community there to mourn the killing of 20 first graders and six educators from Newtown, Conn., President Barack Obama pledged Sunday to start taking action to end the epidemic of gun violence in America.

“We’re not doing enough,” the president said. “And we will have to change.”

“We can’t tolerate this anymore,” he added. “These tragedies must end, and to end them, we must change. We will be told that the causes of such violence are complex, and it is true. No single law, no set of laws can eliminate evil from the world or prevent every senseless act of violence in our society. But that can’t be an excuse for inaction. Surely we can do better than this.” [Scroll down to watch.]

The speech at Newtown High School was the president’s fourth given in the wake of a major instance of gun-related violence. His day had started with a trip to see his daughter, Sasha, at her dance rehearsal at the Music Center at Strathmore in North Bethesda, Md.

“If there’s even one step we can take to save one child, or one parent, or one town from the grief that has visited Tucson, and Aurora and Oak Creek and Newtown and communities from Columbine to Blacksburg before that, then surely we have an obligation to try,” the president told the auditorium.

“In the coming weeks, I’ll use whatever power this office holds to engage my fellow citizens, from law enforcement to mental health professionals to parents and educators in an effort to prevent more tragedies like this,” he said. “Because what choice do we have?”

“We can’t accept events like this as routine,” he said. “Are we really prepared to say that we’re powerless in the face of such carnage? That the politics are too hard? Are we prepared to say that the violence visited on our children year after year after year is somehow the price of our freedom?”