so when do you think he brought the rifle in? Did no one notice an employee carrying a rifle? Were all the victims white? His girlfriend or ex-girlfriend was white. Lots of questions.
Some rifles, such as a AK 47, can have a collapsible stock making it shorter. I have worked at plants where it would be easy to sneak a short rifle in. It could be under a coat or in a cardboard box. Once it is in a locker, no one could see it.