Not saying that the cops were right or wrong, but...
What exactly did the guy have that "appeared to be a gun?" Obviously it wasn't a gun or the cops would be saying that they recovered the guy's gun at the scene. They'd be releasing photos of the gun to prove their side.
So, I wonder what it was...?
Don't know if this answers your question but the last line of the article said "Police say in addition to a firearm, they also found marijuana and other drugs in the car." So, they evidently did find a firearm somewhere.