It's just been removed, but the shooter posted first person cell phone video (two separate videos) of the shootings on Twitter (an account of Bryce Williams). His prior tweets were something about a problem he had with the reporter or cameraman.
The tweets implied that a man named Adam (which matches the name of one victim) reported him to HR for some reason.
That's so incredibly sad and they were so young, too (not that it changes much but didn't barely experienced life as it was). I'm not really sure what to even say. I hope they catch the guy, swiftly, so no one else gets hurt.
This can't possibly be an appropriate story for HN. Please join me in flagging it.