OSHA regulates the demolition industry and enforces standards meant to ensure worker safety. Among other things, its regulations forbid any wall section exceeding one story to stand alone without bracing, unless the wall was designed that way. Witnesses have said they saw a 30-foot section of unbraced wall before the collapse.
A video of the demolition taken the Sunday before the collapse showed bricks raining down on the sidewalk as a worker used a backhoe and claw to remove a second-story front wall.
The sidewalk and the staircase leading up from a subway stop appeared open to pedestrians despite the falling bricks. Cars and trucks could also be seen going past, just a few feet away.