Celebrities are remembering the countless lives lost or changed forever on the nineteenth anniversary of the 9/11 terrorist attack on New York City.

On Twitter, actor Hugh Jackman shared a photo of him wearing a face mask in New York City. "We will always remember 9/11," he wrote.

Alec Baldwin posted a 14-minute long video on Instagram. He shared the somber story of his day in Long Island on September 11, 2001.

Mark Wahlberg shared an image of two lights in the place where the Twin Towers (World Trade Center) originally stood in lower Manhattan. "Today, we honor those we lost on 9/11 and all the first responders, including civilians, who risked their lives to help their fellow citizens," he wrote. "Let’s try to remember that feeling of unity in our country during these difficult times. #UnitedWeStand #NeverForget."

Kelly Ripa posted a photo of the light memorial on her social media accounts. Meanwhile, Katie Couric shared a video of when she learned of the terrorists attacks. She was on-air alongside Matt Lauer and reported the breaking news story for NBC's Today Show.

Candace Cameron Bure, Ciara, Rachel Zoe, Michael Strahan and Mr. T also shared tributes to commemorate the anniversary.

See the social media posts, below.