School officials heard shots in the distance, locked school down before shooter even arrived, or informed by law enforcement.
Shooter rammed truck through school grounds fence

Tehama County Assistant Sheriff says shooter used semiautomatic rifle with multi-round clip. https://t.co/34uU4HvIdG

— NBC News (@NBCNews) November 15, 2017

BREAKING: California sheriff says gunman tried to get into rooms at elementary school to shoot more kids, but lockdown saved lives.

— The Associated Press (@AP) November 15, 2017

side note: NRA gun cultists will be having a fit because sheriff said “clip(s)”