I'm sticking with the facts that I know (or think I know).
1). On Saturday Morning 10/27/18, Robert Bowers shot and killed 11 innocent Jewish people, as they worshiped in their synagogue in Pittsburgh. He injured others, including police who responded to the scene.
2). As he was murdering them, he shouted antisemitic slurs.
3). He had no previous criminal history, or history of diagnosed mental disorder.
4). His social media footprint included a significant number of antisemitic slurs and references to antisemitic conspiracy theories.
5). In January, an account under his name was created on Gab, a social network that
bills itself as a free speech haven. The app, which grew out of claims of anti-conservative bias by Facebook and Twitter, is a popular gathering place for alt-right activists and white nationalists whose views are unwelcome on other social media platforms.
6). Several weeks ago, Mr. Bowers’s account posted a link to the website of HIAS, a Jewish nonprofit organization, which was planning a shabbat ceremony for refugees in locations around the country. The caption read:
“Why hello there HIAS! You like to bring in hostile invaders to dwell among us?”
And hours before the gunman entered the Tree of Life synagogue, the account posted again:
“HIAS likes to bring invaders in that kill our people. I can’t sit by and watch my people get slaughtered. Screw your optics, I’m going in.”
7.) Bowers was not mentally stable. No one, who would take the action that he did, could possibly be mentally stable.
8.) Ideology, white nationalism, and tribalism played a part in his actions. He made that abundantly clear with his posts that I bolded above.