Violent social media posts by the person accused of carrying out the Allen mall shooting praised the “white race,” admired school shooters and hoped for the elimination of Jewish people. Quoting from song lyrics and movies, the 33-year-old’s posts could give a glimpse of what was to come. But the social media account, hosted on a Russian platform, didn’t have much reach or engagement. It resembled a personal diary or blog of an isolated person who distrusted the government and struggled to have relationships with women. The alleged Allen mall shooter who killed eight people and left seven others injured...