President Obama's speech Sunday night at a memorial service for the victims -- mostly children -- of a mass shooting in Newtown, Connecticut was a forceful assertion that the politics surrounding guns (and gun control) must change.

"We can't tolerate this anymore," Obama said. "We are not doing enough and we will have to change." (Full transcript of speech here.)

Obama noted that this was the fourth time in his presidency that he has had to grieve with a community after an incident of mass murder with a gun. But, his speech in Connecticut Sunday was a significant departure from the other addresses he had given to communities torn apart by shooting sprees.

Speaking in Aurora, Colorado just days after a gunman opened fire in a movie theater this summer, Obama was somber, subdued -- and decidedly apolitical. The closest Obama got to making a statement (of any sort) came in the speech's last line in which he said: "I hope that over the next several days, next several weeks, and next several months, we all reflect on how we can do something about some of the senseless violence that ends up marring this country, but also reflect on all the wonderful people who make this the greatest country on Earth."

It was a very different Obama who took the stage at the Newtown memorial Sunday, a president not just saddened by the tragedy but fed up with the lack of forward movement in hopes of preventing the next one.

One sentence in Obama's speech sums up his state of mind. "I'll use whatever power this office an effort aimed at preventing more tragedies like this," he said -- a line the incumbent never came close to uttering in Aurora or, before that, in Tucson in 2011.

What Obama's speech seemed to signal is that, at least in his mind, a tipping point has been reached -- that the slaughter of 20 first graders should not be soon forgotten, that it should mean something.

His critics will note that he offered no specifics as to where he would hope to change laws on guns and that his speech in Newtown, unlike the address in Aurora, came after his second term was assured and he knew he would never need to stand for election again.

Both facts are true. But neither subtract from the fact that Obama could have very easily delivered a speech heavy on empathy and light on anything in the way of a call to action. That he chose to go in a very different direction is a telling indication of his commitment to try to make something happen on gun laws.

Obama's speech Sunday night could be summed up in three words: Enough is enough. Now, can he lead a divided nation to see things his way?

Read more from Washington Post Politics

Obama in Newtown: 'We will have to change'

Will Newtown be a tipping point in the gun-control debate?

What Obama said about guns during the 2012 campaign