She appeared to do this because YouTube decided arbitrary censorship, which demonetized her video content: her decline in viewership and ad revenue is said to be the motivation behind the shooting. Weapon: 9mm handgun.
Police were given warning, multiple times, by the suspect's family . The police questioned the suspect, but let her go the morning before the mass shooting... then police failed to warn YouTube.
Since she was a vegan/lefty, in the most gun-controlled state in the nation (California), there was plenty of warnings that the system failed to act on, and she didn't use an assault rifle, the media has dropped the story almost immediately. There's no value in politicizing a crazed Iranian chick, and the failure of the system to stop her, when they can't divert the story to something like assault weapons bans.
While most outlets all but ignored the story, only giving it passing coverage because it didn't fit the narratives, a few went the extra mile to spin it alt-left:
What support did they offer? The hysterical Giffords Law Center to Prevent Gun Violence "study", that intentionally misleads the gullible to believe that California is one of the safest states for mass murder, by throwing in Suicides, not normalizing for age, and other techniques of propagandists. It is something one could easily ignore, if the media wasn't so damn in your face about the lies, and trying to take every opportunity to undermine the Constitution (2A).
- See something, say something, all they'll ignore everything: