Wednesday marked the fourth anniversary of the tragedy at Sandy Hook Elementary School in Newtown, when 26 children and educators were killed.

In honor of the anniversary, several prominent people released their thoughts and memories of the day.

President Obama, who has previously said it was one of the worst days of his presidency, posted a message on Facebook Wednesday afternoon:

"Four years ago today twenty beautiful children and six heroic educators were killed at Sandy Hook Elementary.

Today, we remember them – the staff and teachers who responded to the danger in their hallways with strength and resolve, guiding the children to safety, even giving their lives to protect the children in their care. We remember the first responders who rushed to the scene to help, holding their own shock at bay because others needed them more. And we remember the children who held each other in the face of unconscionable evil; who, even as they’ve grown up in the shadow of this tragedy, will grow up loved and cared for more fiercely than ever.

Two days after that horror, I traveled to Sandy Hook to tell the people of Newtown that they were not alone – that we shared their grief, that they inspired us, and that for them, we would try to change. That’s all still true. We still share their grief. We’re still inspired by the survivors and the families who have worked to make a difference. And we’ve tried to change. My administration has taken action to tighten the background check system and make it more efficient, strengthen enforcement of existing laws, boost gun safety technology, and help more Americans suffering with mental illness get the help they need. Still, Congress failed to pass gun safety reforms, including universal background checks that had the bipartisan support of the vast majority of Americans, even as more mass shootings have riddled America in the years since. But I still believe that there are enough good people on both sides of this issue who care more about protecting our kids than defending effortless access to guns for those who would do our kids harm. I still believe we have the courage to change."

Connecticut Sen. Chris Murphy, who has been a huge advocate for gun control legislation, especially in the wake of the tragedy, said:

"Today is a hard day. It’s a day of crippling sadness. And a day of impossible, unanswerable questions. I have had the honor over the past four years to become close with so many of the parents and family members of those who were lost that day. Their strength gives me strength. But there is no power that can make the pain visited upon us four years ago fade away.

There’s nothing we can do that will make it right. Our world fractured four years ago and the pieces cannot ever be reassembled the same. But we can promise to be kinder to one another, to hug our loved ones and friends a little tighter, and reach out to those who may need a helping hand. And we can commit to never, ever giving up in the fight to fix our broken laws and make our country safer. No other family should have to endure the pain that too many in Sandy Hook are suffering today, and I won’t rest until our schools and our streets are truly safe."

Connecticut Sen. Richard Blumenthal, another adovcate for gun control, said: Our pain and grief still feel fresh, but so too is our undiminished determination to make the world better and safer in their memory. We stood together that afternoon at the firehouse– and we continue to stand with Newtown, a community that confronted unspeakable tragedy with unimaginable courage and strength. We must never cease striving to stop gun violence, inspired by Newtown’s spirit. Since that horrific day more than 120,000 have perished due to gun violence, and Congress continues to be complicit by its inaction. Undeterred and undiscouraged, we can honor the 26 beautiful children and educators lost that day by resolving to do more and do better.

"Our pain and grief still feel fresh, but so too is our undiminished determination to make the world better and safer in their memory. We stood together that afternoon at the firehouse– and we continue to stand with Newtown, a community that confronted unspeakable tragedy with unimaginable courage and strength. We must never cease striving to stop gun violence, inspired by Newtown’s spirit. Since that horrific day more than 120,000 have perished due to gun violence, and Congress continues to be complicit by its inaction. Undeterred and undiscouraged, we can honor the 26 beautiful children and educators lost that day by resolving to do more and do better."

Rep. Elizabeth Etsy, who serves Connecticut’s 5th District, which includes Newtown, has also been a strong advocate for stricter gun laws. She released a video statement on Wednesday, which you can view here.

Murphy, Blumenthal and Esty joined forces with other politicians in June, in the wake of the mass shooting at Orlando’s Pulse Nightclub, to push for universal background checks and a ban on assault weapons. Murphy held a 15-hour filibuster with Blumenthal’s help, and then Esty organized a sit-in in the House of Representatives.

On Wednesday, Murphy, Blumenthal and Esty were in Washington D.C. with the Newtown Action Alliance, among other gun control advocacy groups, to commemorate the anniversary. They held a vigil of remembrance and mourning at St. Mark’s Episcopal Church on Capitol Hill.

On Thursday, the politicians and advocates will hold a press conference to demand change and educate the public about the toll of gun violence in America. You can view that event live here.