That's a super common pattern. I was thinking of Charles Whitman, but found these too.
- Kip Kinkel (USA, 1998) — killed both parents before the Thurston High School shooting (Oregon).
- Evan Ramsey (USA, 1997) — killed his father before the Bethel High School shooting (Alaska).
- Charles Andrew Williams (USA, 2001) — killed his grandmother (legal guardian) before the Santana High School shooting (California).
- Jeffrey “Jeff” Weise (USA, 2005) — killed his grandfather (legal guardian) and his grandfather’s partner before the Red Lake Senior High School shooting (Minnesota).
- Adam Lanza (USA, 2012) — killed his mother before the Sandy Hook Elementary School shooting (Connecticut).
I'm totally open to both cases being connected, but if you were to suggest it a couple days ago, I'd lean very much against it.
The old adage is "a serial killer intends to get away with it, a mass murderer doesn't, and a spree killer hasn't thought that far ahead."
I've seen a serial killer become a spree killer, but I haven't seen a mass murderer become an assassin, which is its own category. The psychology is very different.
ETA: The math does change if this Brown attack was targeting a specific person, but the issue is all the collateral damage. He could just be a really bad shot though.