1. Did NYMag have access to security video? Or was the detailed description of the range visit

-fiction?
2. Since the parents being
civilly liable for the son's murders would hinge on the parent
knowing their son was dangerous, the prosecution would probably have to
prove they knew that, beyond a reasonable doubt and knowing he was dangerous, provided their son with a weapon plus training practice in using it.
Of course, to DUmmies, just buying the gun and practicing with their son "should" make the parents criminally liable and the range, gun store, and SIG Sauer civilly liable.