News emerged in the wake of the nation's latest school shooting that the FBI had received warnings about the suspect prior to the deadly incident in Florida.

Attorney General Jeff Sessions, remarking on the tragedy the following day, said,

"We can and must do better."

"It is just too often the case that the perpetrators have given signals in advance," Sessions said Thursday. "We've had advance indications, and perhaps we haven't been effective enough in intervening immediately to deal with that. I suspect it appears that we've seen that again in this case."

But law enforcement faces serious challenges in preventing frequent, high-profile gun violence, even with some alerts from the public and warning signs lurking on social media.

One of the foremost challenges: Threats pour into the FBI constantly.

"I don't even know how to quantify it," said former FBI special agent Josh Campbell, a CNN law enforcement analyst.

The difficulty of sussing out usable information from myriad threats is further compounded by the reliability of the warnings, the strength of existing law enforcement information, the public's ability to discern what is cause for concern and instances where law enforcement powers butt up against civil rights.

Connecting the dots

While initial reports stated the FBI was following up on two alleged threat reports, a law enforcement source tells CNN's Evan Perez that authorities believe they have only identified one threat report, which was in the form of a screenshot of a YouTube user with the suspect's name who said, "Im going to be a professional school shooter."

Campbell said the office that received a threat could search the FBI's database, and that the agency's ability to follow up from there would hinge on "what level of credibility and specificity" it can determine.

The FBI special agent in charge of the Miami division, Robert Lasky, said Thursday that the bureau had received a tip about the YouTube comment last year, but that FBI database reviews and checks were "unable to further identify the person."

CNN legal analyst Carrie Cordero said the FBI's inability to link the comment to the eventual suspected shooter was reason enough to ask questions about what might have gone wrong.

"No one wants to criticize law enforcement when they're in the moment of responding to a major event like this," Cordero told CNN's Brooke Baldwin. "But there are legitimate questions about what they knew about the individual and whether they took all of the steps that were available to them."

Unless the FBI can identify the person, Campbell said, its options for moving past that point were nil.

"An FBI investigation is only as good as the information that comes into the FBI," Campbell said.

Asked if, given all these challenges, the FBI ever prevents a shooting like the one in Florida, Campbell said successes are difficult to assess and that in many ways it would be trying to prove a negative.

"It's hard to quantify something you interdict, something you stop," he said.

The government's investigative powers also can come into conflict with civil liberties and due process concerns. Law enforcement needs to demonstrate probable cause to obtain a warrant, mental health professionals and the mentally ill have privacy rights, and the Second Amendment has led to limits on how the government regulates firearms.

Read the full story online at stylemagazine.com.