Without a closer inspection, I'd say it's perfectly plausible that the gun pictured in the article would be capable of discharging a projectile. Perhaps it's quite obvious when you look at it up close from several angles, but that was the TSA employee's point... it if was being used to threaten someone, they wouldn't necessarily be able to take the time to examine it...
As an example, here's a gun that's very similar in size to the prop, that is quite capable of killing you (and four of your friends):
As an example, here's a gun that's very similar in size to the prop, that is quite capable of killing you (and four of your friends):
http://www.impactguns.com/data/default/images/catalog/535/na...