this could technically be faked, as with anything on the internet but then again...
for context:
the shooting occurred around noon local time of September 10th, unless i somehow have my timezones mixed up
on September 9th, one day before, a book was posted for sale called "The Shooting of Charlie Kirk: A Comprehensive Account of the Utah Valley University Attack, the Aftermath, and America’s Response"
the page was taken down by amazon, whether this was by amazon or not is unconfirmed. amazon admitted it does exist, but the date got "set wrong". extremely unlikely, very suspicious
there are still links for it on archive sites
https://archive.ph/1VLF3