There is a building close to where this explosion happened that was the Nation of Islam temple in Harlem back in the 1960s. After Malcolm X was assassinated, his supporters sought revenge and set a bomb off that blew the top floor off the building. The NOI simply installed a new roof on what had been the floor of the top floor and the building stands today one story shorter than it was originally built.
Whenever a building explosion happens in Harlem, the first though of most people in Harlem goes back to that event.