They are scratching for anyone, or anything else to blame but their son. First, you had the excuse of “well, we contacted the police about him, they must not have done their jobs” line of argument. This fails when you consider that the actual threatening video was posted online only on the day of the horrific crimes he committed. Second, the murderer’s family tries mightily to shift blame to the NRA, anti-gun control politicians and anyone else they disagree with politically. The bottom line remains that their son came from the very weird Big Hollywood “culture” and he had talked extensively of watching porn online.
The killer posted numerous videos online. Some were voluntarily removed by the creep (by his own admission in his writings) AFTER the police paid a visit (he didn't want them to be tipped off to his plans too soon and was relieved that they did not enter his residence).
If he made a "terrorist threat" in his videos, that would have been sufficient to haul him downtown.
It is unclear if Youtube removed any of the videos for violating "community standards" and if they did, did youtube.inc bother to note anyone with legal authority to follow up? The police visit was because of a call from his stepmother (whom he planned to kill, along with his half-brother).