What if a gamma-ray burst hit the high frontier?

One of the wonderful things about space settlement is its resistance
to disaster. With several independent habitats, it is very unlikely
that any problem will be a disaster to all of them at once, which
means the ones less affected will be able to help those more affected
so everybody wins. Moreover, disasters we are used to here on Earth
would be rare in space, such as storms.

There is one event that comes to mind that I think might be able to
destroy a high frontier civilization though: a gamma-ray burst from a
dangerously close supernova.

* it would affect a large area of space, so habitats being in various
orbits wouldn't necessarily save them. The disaster hits everybody at
once.

* while habitats would have shielding for cosmic rays, they would be
unlikely to be able to handle the energy these put out in such a short
amount of time... I think...

* a GRB would also cause a lot of damage on Earth, so even low Earth
orbit habs are in a lot of trouble with diminished odds of getting
help

Now, of course, such events are very, very rare, but what, exactly, do
you think the damage would be? How effective would the every-day
radiation shielding be against this burst? Would the habitat
themselves be in jeopardy, or just the environment inside? What about
things like computer equipment?

I, honestly, don't even know where to begin on calculating these
things, which is why I'm asking here... just my gut tells me that this
much ionizing radiation in such a short amount of time can't be good
news.

Is there any practical effort they could make to mitigate the risk?
Considering the rarity of these events, is there anything they
*should* do?