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It was forbidden. But the group of friends sneaked into Fordham University’s most recognizable building in the dead of night anyway early Sunday.

They clambered up the steep staircase of the granite bell tower that overlooks Fordham’s Rose Hill campus to take in the view of the Bronx under moonlight, sending a Snapchat video from the top.

Then something went horribly wrong.

One of the students, a 22-year-old senior, fell through an opening in a landing, the police said, and plummeted down the inside of the clock and bell tower just a month before her graduation.