Dude, if I saw some guy walking around with what looked like a gun in a store, I'd be nervous too. Who walks around with a gun in a Wal-Mart? People are crazy, so it's not safe to assume anything. All I'd know is there's a dude with a gun in a place where people don't normally carry guns. That is very legitimate cause for concern. If he'd shot the store up Columbine-style then people would be asking why nobody did anything about something that was so obviously an apparent threat, and somebody's head would roll over it, cause everybody would be asking "Why wouldn't anyone do anything about a guy with a gun in a Wal-Mart." Yet because he didn't then people aren't treating it the same simply because they have the luxury of hindsight. And it's not like it looked like a toy gun. It looked like a military grade assault rifle. **** nervous. I'd have been terrified.
It might not be black and look like it's made out of what I'd consider "gun material", but I've seen guns that looked like they were made out of some weird material with some weird colors, so I'd have to be an idiot not to worry about it.
And even if he did tell the cops it was fake, they'd be negligent to just say, "Oh, well, he said it was fake, so everything's okay now. Carry on, citizen." No. There's a guy holding a gun and you can't take chances just on his word. He had a gun out in a store for no apparent reason. That doesn't scream reliable. If I was a cop and this guy was holding what may very well have been a dangerous weapon, and he didn't put it down when ordered to, I'd have shot him too.