In an interview with ABC News' Dr. Richard Besser, President Obama invoked the horrific slaying of children at Sandy Hook Elementary to shame Congress for not acting on gun control issues.

From ABC News:

You know, those two or three days after the Sandy Hook shooting are some of the worst days of my presidency because I met those families right after. And you're talking about 6-year-olds who were just systematically murdered. And that may be one of the few times where I was just shocked that Congress didn't act.

Obama said this in response to Besser reminding him that more than a year has passed since the shooting death of those 20 children and six adults and yet there is still no new gun control legislation.

"What we've done is to try to do as much as we could administratively to tighten up how background checks are run, to go after illegal drug runners," Obama said. "But I will tell you that trying to get something through Congress has proven to be very difficult. And it's heart-breaking."

The president continued:

But the power of NRA and the gun lobby in Congress is formidable. And you know, we're going to keep chipping away at this, but until you get intense public demands for this, it's probably not going to happen because some special interests and lobbyists in Washington are really, really strong and their membership feels very intensely about the issue. Whereas the general public is concerned about it, but doesn't make it their top priority.