Help! What is this black stuff killing my customer's trees?

[Xylic]

Hello-

I have a customer that is asking me what is wrong with his tree that is killing it from the top down and how to stop it and save his tree. These are Cedar Elms fyi. It is like a black fungus as you can see, but I am unsure what it is exactly. I am located in the central Texas area. Any idea what this is and how to stop it?

 

[B Harrison]

Not so sure that's what killed the tree. Take a picture of the base of the tree and a wide angle of roots or ground at base.

Cant see much in your first two pictures if there was something to see other than no leaves.