LOS ANGELES-Lady GaGa, Kim Kardashian and Oprah Winfrey were among the many celebrities who took to Twitter to remember the events of 9/11 on Sunday.

As Americans paid tribute to those who lost their lives 15 years ago, the stars joined the masses to offer their thoughts.

Kardashian recalled, “15 years ago today I remember my dad calling me waking me up to tell me not to come into the office & told me what happened in NYC.”

She posted an image of the Manhattan skyline without the Twin Towers, which crumbled on 9/11, and added: “We then had a family meeting at my moms (sic) & prayed. Life is so precious & I pray for everyone who was affected by this awful tragedy. #NeverForget911.”

New York native Lady GaGa offered up a solemn tweet, writing: “God Bless all the men and women who died in the attacks or fight to save lives during the Sept. 11 attacks #WeWillNeverForget #NewYorker.” Taylor Swift, Reese Witherspoon, Kerry Washington, Willie Nelson, Carole King, the Backstreet Boys, Desiigner, Shannen Doherty, Heroes star Masi Oka, and Jessica Chastain also remembered those who lost their lives, while Oprah tweeted: “15 years... Don’t we all remember exactly where we were when we heard or saw the second plane hit the Tower?! #NeverForget.”

Meanwhile, U.S. presidential candidate Hillary Clinton, who also posted a tribute to the fallen early on Sunday, was forced to leave a Ground Zero, New York ceremony marking the 15th anniversary of the terrorist attacks early before after falling ill.

A campaign spokesman has told the media the former First Lady became “overheated” at the event, adding, “She departed to go to her daughter’s apartment, and is feeling much better.”