The tipster apparently gave them every detail of the nightmare to come — Cruz was homicidal, he had a gun, he was telegraphing his intentions on social media. The caller even knew that he was interested in shooting up a school. That means the FBI was informed not once but twice in the span of a little more than three months that someone named “Nikolas Cruz” was a threat to public safety. (The infamous YouTube comment in which someone posting as “Nikolas Cruz” said he planned to be a “professional school shooter” was left on September 24.)

Nothing happened. And so a horrendous attack is now also a horrendous scandal.

I wonder if the FBI’s already damaged reputation will ever recover.

Who was the caller who knew Cruz’s plans so well? I thought he had no friends. Was it a member of the family he stayed with after his mother died last fall?

The FBI was directly warned twice but local law enforcement had known for years that Cruz was “troubled.” CNN reported this morning that deputies visited his home no fewer than 39 times(!) since 2010 for problems including “a mentally ill person, child/elderly abuse, a domestic disturbance and a missing person.” Records don’t indicate which resident in the home was the cause of their visits but I haven’t read anything in the last few days suggesting that his mother or brother had trouble with the law. (His father passed away years earlier.) Most of those visits, if not all, were likely aimed at Cruz. He reportedly would introduce himself to people sometimes by saying, “Hi, I’m Nick. I’m a school shooter.” The next-door neighbor remembered that he “would sometimes be hitting his head and covering his ears.” Once, when she sent him home after misbehaving at her house, he returned with a golf club and smashed her trailer. He bought his AR-15 just three days after leaving school last January.

Reporters asked the FBI yesterday, before news of the missed January 5 tip emerged, why they didn’t act on the YouTube comment last fall. WaPo:

Without more to go on, officials felt there wasn’t enough legal justification to issue a subpoena to YouTube for the underlying information about the “nikolas cruz” who had threatened a school shooting, a law enforcement official said…

Hosko, the former FBI assistant director, said the FBI gets more than 100 threat reports each day, in addition to other reports of mental health and other issues. That leaves supervisors in the difficult position of deciding how many resources should be devoted to each case and for how long. Even in terrorism cases, Hosko said, the bureau sometimes has to leave suspects unmonitored because the FBI lacks personnel to follow each of them all the time…

Hosko said in most cases of possible threats, an early question supervisors ask is, “At the end of the day, would we even have a federal crime if we proved a person sent this or posted this?” And in Cruz’s case — where the comment is a not a specific threat — the answer was probably no, he said.

That was a defensible position yesterday. Unless you want a Chinese surveillance state, you can’t go chasing after every crank in the YouTube comments section. How many man-hours would you want to invest in hunting down someone who farted out something about a school shooting, only to find he’s a troll with a sick sense of humor? “Without more to go on,” the YouTube comment wasn’t alarming enough in its own right to warrant an FBI scramble.

But it turns out they did have more to go on, didn’t they? And remember, the report of the YouTube comment must have been saved somewhere in the FBI’s system because agents showed up to speak to the man who reported it last September within hours of Wednesday’s massacre. If Cruz’s name was in a database, why didn’t the January 5 tip about him get cross-checked with that database? Two independent reports of Cruz’s designs on shooting up a school surely would have set off alarm bells. Those alarm bells would have led them to inquire more broadly about Cruz, which would have turned up 39 police visits and the purchase of an AR-15. Would all of that have been enough for probable cause sufficient for a search warrant? Seems possible.

Here’s where I point you back to my post yesterday speculating that the effort to end school shootings will ultimately focus not on gun-grabbing or mental-health treatment but on greater surveillance and data-collection aimed at “troubled” people. People will look at all of the red flags I just noted and wonder why they weren’t collected somewhere centrally; each individual red flag is one tile in the mosaic, not necessarily dangerous in itself, but step back and look at the mosaic itself and it’s a portrait of mass murder. Not coincidentally, the sheriff of Broward County appealed explicitly to the government yesterday to give law enforcement the power to detain and commit people based on disturbing social media posts. “People are going to be rightfully so concerned about their rights, as am I, but what about the rights of these students?” he said. That’s the debate that’s coming.