To my very untrained eye it looks like cracked glass substrate.
The question is why it cracked. It does not look like it cracked by pressing something on the screen. In that case I would expect a star shaped crack.
Perhaps the frame was twisted, or perhaps the glass substrate was not seated properly in frame and cracked or the glass might have had a flaw.
It is very difficult to judge from a relatively low resolution photograph. You will have to take it apart and see. Even then it might be impossible to judge. What if the glass had a flaw before installation?