https://apod.nasa.gov/apod/ap221015.html
Image of the same event from the Fermi LAT.
The Fermi GRB is one of the instruments listed in the article as detecting the initial burst and would had generated a redirection request for a whole family of different telescopes, including Fermi itself.
Actually, this is a better page with both the swift and fermi images.
https://www.nasa.gov/feature/goddard/2022/nasa-s-swift-fermi...
" In low Earth orbit Fermi’s Large Area Telescope recorded gamma-ray photons from the burst for more than 10 hours as high-energy radiation from GRB 221009A swept over planet Earth last Sunday, October 9. "
while the second is more specific: "the afterglow of GRB 221009A faded over the course of about 10 hours."
Related interest: The Earth's atmosphere itself produces gamma flashes up to 20MeV:
https://en.wikipedia.org/wiki/Terrestrial_gamma-ray_flash
And: "Possible Role of Gamma Ray Bursts on Life Extinction in the Universe" (abstract only):
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.11...