I was shooting two weeks ago and something similar happened to me with 5.56 ammo.
The rifle fired fine and then the bolt hung up. I looked to find the front half of the case sticking upright from the action in front of the bolt. Never found the back half, but it must have ejected like it was supposed to.
Had the front half remained lodged in the chamber, it would have ended in the same result as your photo. Luckily for me it had extracted and was not lodged, so no broken shell extractor was needed.
I was firing some reloads that I bought at a gun show. They were made with LC brass by a local manufacturer, who I have dealt with a lot and who has an excellent reputation. This is the first time I had fired any of his rifle loads. I'm sure the case must have been stressed too much previously or something that caused it to break in half when fired.
Edit: I just went down and dug the case out of the trash can. Here is a really bad cell phone picture of it.
