Fireblight? Phytophthera infection? Need to know what symptoms it displayed before it died. If it looks like its been burnt, or is orangey brown all over, could be fireblight.

I'd be ever so pleased, and then plant something more attractive! As Bamboo says above, although possible it got old in a tough position and just gave up.

Pyracantha can be very attractive - horses for courses!

I agree steragram. Are there signs of other trees shrubs dying? any large honey coloured toadstools around the stem of the shrub? if yes it could be a species of honey fungus killing it.