When was the last shooting in the US that involved a "ghost gun" or a gun purchased at a gun show from a private vendor?
shilo, this is an excerpt from your news link; "Boulder Police Chief Maris Herold confirmed Friday the suspect used the Ruger AR-556 pistol in the attack, which she said he purchased at a gun store in Arvada, Colo. The weapon appeared to fool police who responded to the shooting as they referred to the gun repeatedly as a rifle or AR-15 styled rifle in a charging affidavit"
It was neither a "ghost gun," nor purchased from a private vendor at a gun show.