Lady Gaga saw the Twin Towers collapse

From the roof of her school when she was 15.
In an exclusive radio interview, the pop queen recalled her father, Joseph, coming to collect her from the Convent of the Sacred Heart in Manhattan, New York on foot on the historic day.
The worried pair then waited in fraught desperation for 10 hours before they finally learnt that Gaga’s mother was safe. The mother of Gaga, Cynthia, worked across the street from the World Trade Center.

"The whole city was covered in ashes," Gaga told radio host Toby Knapp on Washington DC's Hot 99.5.

Gaga, now 25, said she experienced conflicting feelings after Osama bin Laden had been killed.

"It's a difficult thing,” she said. “Nobody wants to celebrate anyone's death. But I know it was something that meant a lot to the people of New York, especially those who lost loved ones that day."