Shooter in southern California attack knew his victims and how to trap them, police say

Suspect chained the front and rear gates of the office complex, then was seen on security video brandishing a semiautomatic handgun

A gunman who killed four people, including a 9-year-old boy, in a rampage at a southern California office building knew all the victims and his motive may have involved personal or business relationships, police said.

This was not a random act of violence," said Orange police Lt Jennifer Amat on Thursday of the attack at a two-story building that housed small businesses in Orange, southeast of Los Angeles.