Obama Speaks at Interfaith Vigil in Newtown, Connecticut

WASHINGTON —  U.S. President Barack Obama has vowed to use all his power to make sure that tragedies like Friday's killing of 20 children and six adults at an elementary school are never repeated.

Obama joined mourners Sunday night in the northeastern town of Newtown, Connecticut where a gunman's rampage killed the 26 people. He told those gathered for a nighttime vigil for the victims that they are not alone in their grief. The president said people across the country are mourning with them.

Obama said the nation is left with hard questions after the shooting. He noted this was the fourth mass shooting incident that has occurred since the start of his presidency almost four years ago.

"We can't tolerate this anymore. These tragedies must end, and to end them we must change. We will be told that the causes of such violence are complex, and that is true. No single law, no set of laws can eliminate evil from the world and prevent every single act of violence in our society. But that can't be an excuse for inaction."

Earlier in the evening, the president met privately with the families of those who lost loved ones at Sandy Hook Elementary School, and to thank the first responders to the tragedy.

Grieving residents of Newtown, Connecticut flocked to places of worship Sunday. Robbie Parker paid tribute to his six-year-old daughter, Emilie, who was gunned down at Sandy Hook Elementary School.

"She was an exceptional artist. And she always carried around her markers and pencils, so she never missed an opportunity to draw a picture or make a card. She was a mentor to her two little sisters, delighting in teaching them how to read, dance, and find the simple joys of life," said Robbie Parker.

Parents of surviving students share in the heartbreak. Lynn Wasik, whose daughter Alexis studies at Sandy Hook, spoke on Fox News Sunday.

"I think I am still very numb," she said. "There is no way to make any sense of anything this person has done, not only to families, but [also] to a community, to a nation."

The shooter, 20-year-old Adam Lanza, is believed to have killed his mother at home before shooting his way into the school.

Accounts of heroism have emerged, of unarmed school administrators and teachers rushing Lanza and placing their bodies between the gunman and panicked children in their care.

Lanza, who was armed with guns belonging to his mother, took his own life after a 10-minute rampage at Sandy Hook. It was the latest in a series of mass-shooting incidents the United States has suffered in recent years, one that has sparked calls for tighter restrictions on firearms in the United States.

Democratic Senator Richard Durbin spoke on Fox News Sunday.

"Are there guns that really should not be sold across America? Military assault weapons, such as the one that was involved in this horrific incident in Connecticut? Are there high-capacity ammunition clips that really have no value whatsoever when it comes to sporting, hunting, even self-defense?" asked Durbin.

Gun rights supporters say the answer is not to infringe on Americans’ right to bear arms. Republican Congressman Louis Gohmert, who also appeared on Fox, said, "A free people should be an armed people. It ensures against the tyranny of the government," he said.

Gohmert argued that the problem is not a nation awash in firearms, but a citizenry that is not armed enough. He said lives could have been saved at Sandy Hook if teachers carried guns to school.

"Hearing the heroic stories of the principal, I wish to God she had had an M-4 [assault rifle] in her office. So when she hears gunfire, she pulls it out, so she would not have to lunge, heroically, with nothing in her hands," he said.

About half of U.S. households have at least one gun. There are more than 200 million privately-owned firearms in the nation. Friday, President Obama spoke of the need to address gun violence, but did not lay out any immediate recommendations for doing so.