President Barack Obama on Sunday memorialized the victims of the Washington Navy Yard shooting by calling for a transformation in the nation's gun laws to address an epidemic of gun violence, saying, "There's nothing inevitable about it."

Reprising his role of the nation's consoler in chief after yet another mass shooting, Obama said Americans should honor the victims of last Monday's shooting by insisting on a change in gun laws. "It ought to obsess us," Obama said.

"Sometimes I fear there is a creeping resignation that these tragedies are just somehow the way it is, that this is somehow the new normal. We cannot accept this," Obama said.

He said no other advanced nation endures the kind of gun violence seen in the United States, and blamed mass shootings in America on laws that fail "to keep guns out of the hands of criminals and dangerous people."

Urgent: Support Obama's Gun Ban Plan? Vote in Poll

"What's different in America is it's easy to get your hands on a gun," he said. He acknowledged "the politics are difficult," a lesson he learned after failing to get expanded background checks for gun buyers through the Democratic-controlled Senate this spring.

"And that's sometimes where the resignation comes from: the sense that our politics are frozen and that nothing will change. Well, I cannot accept that," Obama said. "By now, though, it should be clear that the change we need will not come from Washington, even when tragedy strikes Washington. Change will come the only way it ever has come, and that's from the American people."

Obama joined military leaders in eulogizing the 12 victims killed in last Monday's shooting, speaking from the parade grounds at the Marine Barracks, a site personally selected by Thomas Jefferson because of its close marching distance to the Navy Yard. The memorial service came on the first day of fall, which shone brightly in Washington, with sun sparkling off the instruments being played by the Navy Band and the gold dress uniform buttons worn by so many in the crowd.

The invitation-only crowd included around 4,000 mourners, with the victims' tearful, black-clad family members directly in front of the speakers' stage. The president and first lady met privately with the families before the service, White House officials said.

Authorities say their loved ones' lives were taken Monday by shotgun-wielding Aaron Alexis, a 34-year-old former Navy reservist and information technology contractor who struggled with mental illness. Police killed Alexis in a gun battle.

By the end of the day, the Senate's chief gun control proponent, California Democrat Dianne Feinstein, was calling on her colleagues to restart the debate on gun control and "do more to stop this endless loss of life." Obama didn't speak out on the issue until Saturday night, when he urged a Congressional Black Caucus Foundation dinner "to get back up and go back at it" to push gun control legislation that stalled in the Senate earlier this year. Obama proposed the legislation in the aftermath of the elementary school shooting in Newtown, Conn., that killed 20 first graders and six staff.

Obama said it's clear from the Navy Yard shooting that the country needs to do a better job to secure its military facilities and improve mental health services, but also address gun laws.

"Our tears are not enough," Obama said Sunday. "Our words and our prayers are not enough. If we really want to honor these 12 men and women, if we really want to be a country where we can go to work and go to school and walk our streets free from senseless violence without so many lives being stolen by a bullet from a gun, then we're going to have to change."

The military leaders who spoke before Obama at the memorial service, including Defense Secretary Chuck Hagel, Navy Secretary Ray Mabus and Adm. Jonathan Greenert, chief of naval operations, avoided any mention of gun control. But Washington Mayor Vincent Gray spoke forcefully for action, mentioning that one of the Navy Yard victims, Arthur Daniels, had already lost his 14-year-old son to gun violence and citing a string of mass public shootings in recent years.

"Why is it that these tragic consequences and these tragic occurrences never seem to move us any closer to ensuring that guns don't get into the hands of criminals or mentally unstable people?" Gray asked. "I don't know the answer. But I do know this — that this time it happened within the view of our Capitol dome, and I for one will not be silenced about the fact the time has come for action."

Urgent: Support Obama's Gun Ban Plan? Vote in Poll

The service ended with a bugler playing taps and singing of the Navy hymn after a reading of the names of the fallen, who ranged in age from 46 to 73 and included civilian employees and contractors. Eight people were also hurt, including a police officer and two others who suffered gunshot wounds.

Obama also mentioned each victim, and said memories of them will go on, along with "the sense that this has happened before."

"What wears on us, what troubles us so deeply as we gather here today, is how this senseless violence that took place in the Navy Yard echoes other recent tragedies," he said. "As president, I have now grieved with five American communities ripped apart by mass violence: Fort Hood, Tucson, Aurora, Sandy Hook and now the Washington Navy Yard. These mass shootings occur against a backdrop of daily tragedies as an epidemic of gun violence tears apart communities across America, from the streets of Chicago to neighborhoods not far from here."

© Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.