The cops said they found an "AR-styled assault rifle also known as a ghost gun", what does that mean? Was it an unserielled gun or not? And I assume it isn't an actual "assault rifle" with a firing selector.
US cops are so untrustworthy to start with, saying nonsense like that shows them as completely incompetent.
Someone very likely 3d printed an AR lower (unserialized, therefore a "ghost gun"), unlikely it had an autosear. The news and police typically call disfavored semi-auto weapons "assault rifles" and things that are fully automatic "machine guns".
This newer incident likely won't be as controversial since the riders had actual weapons, not toys; and no claim that the Waymo "imprisoned" the riders, as many people seem to have previously hallucinated.