"According to Las Vegas police, officers were called to 801 S. Pavilion Center Drive at 12:47 p.m. by a store worker who said a man was destroying merchandise. Police were told the man had a gun. Capt. Patrick Neville described Scott as "kind of going berserk."
http://www.lvrj.com/news/slaying-of-army-veteran-shocks-friends-98223884.html
I can't help you any further if you can't even bring yourself to read the basic news accounts.
Apparently you have the comprehension problem. It was the police captain who described the victim as going berserk, not the Costco employee. Your own account shows that Costco simply reported a man destroying merchandise, which he seems to have been doing, and that he was armed.
Don’t waste your time on him, just ask him, he’s always right. He’s also a liberal.