The first man gave the window two whacks with no luck. On the third try the head of the rescue hammer broke apart - it looked like the metal insert just broke off and fell to the ground.
With those hammers a whack is often a mistake. When the insert hits the window in the right angle, a flick from the wrist is enough to break tempered glass.
I still prefer the Resqme for the smaller package and option to easily carry it.