New York City Mayor Bill de Blasio on Friday blamed his absence at a 9/11 memorial ceremony on his staff not letting him know about the event.

The solemn dedication ceremony honoring those who died from toxic exposure at Ground Zero after the September 11th terrorist attacks took place Thursday morning at the 9/11 Memorial Glade at Liberty and West streets. Both de Blasio, who is running a long shot campaign for president, and Democratic Gov. Andrew Cuomo (N.Y.) were absent from the ceremony, according to the New York Post.

"The Mayor’s team believed they could not make the event work with his schedule and declined without conferring with him," de Blasio spokeswoman, Freddi Goldstein, said in a statement. "Had [he] known about the invitation, he would have attended."

Cuomo expressed regret during an event in Manhattan, saying, "I regret that I couldn’t attend…You know, we supported that memorial, I think we gave them $500,000."

Attendees at the memorial were not happy about the absence of Cuomo and de Blasio. Maureen Fritz attended the event to remember her brother, firefighter William Gormley, after he passed away in 2016 from an illness related to the 9/11 attacks. Fritz slammed de Blasio and Cuomo for not appearing at the memorial.

"They should have been here and it’s unacceptable that they’re not," Fritz said. "They ought to be ashamed of themselves . . . They should not be reelected at all because that’s not how you treat your citizens, your first responders."

Michelle Holfester lost her husband, Det. William Holfester, in 2008 from cancer related to clean up efforts at Ground Zero and did not buy excuses about the absence of de Blasio and Cuomo.

"They should have been here, that’s the bottom line," she said. "We’re here where are they? They’ve seen through the years what’s been going on the suffering with the men and women that lost their lives post 9/11 … It’s not a good picture. It doesn’t look good."

While Cuomo and de Blasio were absent from the event, former New York City Mayor Michael Bloomberg, who is chairman of the memorial museum board, and former Daily Show host Jon Stewart were in attendance.