[TheRealEdAbbey]

A GRB hitting earth wouldn't actually cause an immediate extinction event. From Wikipedia:

> Earth's atmosphere is very effective at absorbing high energy electromagnetic radiation such as x-rays and gamma rays, so these types of radiation would not reach any dangerous levels at the surface during the burst event itself. The immediate effect on life on Earth from a GRB within a few parsecs would only be a short increase in ultraviolet radiation at ground level, lasting from less than a second to tens of seconds. This ultraviolet radiation could potentially reach dangerous levels depending on the exact nature and distance of the burst, but it seems unlikely to be able to cause a global catastrophe for life on Earth.

https://en.m.wikipedia.org/wiki/Gamma-ray_burst

The long-term effects are what could kill us, namely, the destruction of the ozone layer.