From that link:
“#texaschurchshooting shooter is 29 year old US marine turned muslim convert, Samir Al-Hajeed. His manifesto is making its rounds on the web”
Maggief, a name to check. .... Samir Al-Hajeed
UPDATE
https://archive.4plebs.org/pol/thread/148125868/
Santa Monica Observer is a rumor mill site....
Santa Monica Observer is a rumor mill site...
https://archive.4plebs.org/pol/thread/148125868/
I did a search on that Arabic nmae Samir Al-Hajeed