Egg bound hen dies

We have had a traumatic experience with one of our best layers. At 16.00 we noticed for the first time she had a muckky bottom and was walking legs apart. Recognising this we gave her olive oil orally and in the vent and it was easy to feel a large mass of egg but no shell. She could not pass this mass despite the oil and very quickly died. It was very distressing as this was quicker than we thought. I read that diet can bring this on- she was not a new layer, nor old, the hens all eat the same and I dont think she was fat. Its a mystery- a friend says this can happen and others say they have never seen it. Its our first death since we had the hens a year ago but I read after that a warm bath can help. A friend said that where there is a large mass a bath would not help. What did come out looked like the egg had been boiled -perhaps due to the body heat?? I hate to think we missed something as it was quite upsetting for our son too. All the hens eat pellets and the others are fine. It has recently got warm after a very icy cold winter- any ideas?

Hattie I have removed your other post as it says exactly the same thing, somebody may come up with a reason for your problem, but once again so sorry xx