People are saying the "manifesto" is fake, because of the time it was posted.
Some of Texas is on CDT, but El Paso is on MDT. UTC-6

It's 1:59 Now in California, in PDT (UTC-7)
The thread it was posting in was archived on archive.org
https://web.archive.org/web/20190803162950/https://8ch.net/pol/res/13561044.html
The time listed there is 2019-08-03T16:20:32Z, Z means UTC/GMT, so that's 10:20:32 MDT.
El Paso Police first Tweeted at 11:03 MDT (17:03 UTC)
Source: https://twitter.com/EPPOLICE/status/1157698560126857217
Some local media reports the shooter entered at "10AM" (Presumable MDT), which confuses matters. :
https://www.ktsm.com/news/breaking-possible-active-shooter-at-walmart-near-cielo-vista-mall/
However other local media puts it at 11AM MDT
https://www.elpasotimes.com/story/n...ista-mall/1910012001/?cid=twitter_elpasotimes
As does this:
https://kfoxtv.com/news/local/el-paso-police-respond-to-active-shooter
And mainstream media is now getting the time right:
https://www.foxnews.com/us/el-paso-walmart-shooting-multiple-fatalities-suspect-in-custody
https://www.nytimes.com/2019/08/03/...tion=click&module=Top Stories&pgtype=Homepage
So I think we can conclude the manifesto was posted at 10:20 MDT, and the shooting around 11:00AM MDT. Police response to multiple calls of a shooter in a city is very rapid, and they tweeted a "stay-away" active-shooter warning at 11:03
The issue here is that people will claim that a fake manifesto indicates some kind of false flag operation. The complexities of timestamps and time zones, and the initial confusion over the time, is going to give that theory legs.