Great Molasses Flood
Because the molasses was sticky, people in it could not get out. When the tank first broke, some of the molasses was still hot, so it moved fast at first. But it cooled down quickly in the cold winter air.  So people and other animals fell into warm, soft molasses that got hard around them, and they could not get out.  When it covered people's noses and mouths, they could not breathe.