The History Channel has a thing on GRB’s. According to that program the big one’s are caused by massive, short-lived stars going “hyper-nova”, mainly to be found in young galaxies made up of such stars.
It’s the small version—the binary Neutron stars merging—that happen in galaxies like the Milky Way and which present more of a threat to us.
The program implicated such a blast, nearby, in the Ordovician mass extinctions.
-- Marvin
I suspect a warning could be issued by the government to warn the populous.
I have many contingency plans on how to survive such an event, not to give away too many secrets but by hiding behind my sister in laws butt would all but ensure my survival.
And no, I won't tell you her name.