You press yourself even closer into the glass as the gunman notices you. You cower in the corner and hope. He lines up the gun and shoots.
It misses.
Instead of an explosion of pain, you feel nothing. Part of you registers the sound of glass shattering so loudly it may as well be exploding from inside you.
That is when you realize what's happened.
The glass that held all your weight has fallen away. You are falling, too.