I remember learning about this. I wonder if Earth was enveloped in such a burst, if we'd go out quickly, peacefully, like a heart attack in our sleep. Most life wiped out on our planet in an instant. It makes you wonder how many world out there contain the empty structures of civilizations that went out in an instant, with a whisper.
I think that on average, there's a GRB close enough to us to matter once every billion years or so. However, it'd still need to be aligned perfectly to hit us, making the actual extinction event far less likely.