Breaking News Emails

Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.
 / Updated 
By Amanda Sakuma

The red flags that checkered Omar Mateen's life — a pair of FBI investigations, alarms raised by family and former colleagues — stacked up over the years.

And yet, Mateen was able to legally buy an AR 15-style rifle and a 9mm handgun just days before he carried out one of the deadliest shooting massacres in modern U.S. history.

There was a disconnect between the warning signs in Mateen's recent past and the ease of his ability to buy powerful weapons. It deepens the tragedy of his shooting spree at an Orlando gay night club over the weekend, which claimed the lives of 49 innocent people and wounded 53 more. But even in hindsight, few barriers would have likely prevented the gunman from carrying out the attack.

Orlando Police identified the suspect in the Pulse Nightclub shootings as Omar Mateen, 29, a U.S. citizen born in New York.via Orlando Police

In this new era of homegrown terrorism and mass shootings, there are glaring gaps in the United States’ model used to combat the full spectrum of extremism. Federal authorities frequently keep tabs on a network of individuals identified as potential terrorist sympathizers. Yet there's no universal approach toward de-escalating extremism outside of the criminal justice system. Short of catching a person actively conspiring to break the law, options are limited for families or even law enforcement to intervene before it's too late.

Federal agents launched a 10-month investigation into Mateen in 2013 for espousing Islamic propaganda at work. They opened a second inquiry just months after the previous one concluded, probing a potential link to an American citizen-turned suicide bomber in Syria. The FBI’s conclusion: 29-year-old Mateen, born in New York, did not pose as a violent threat.

Related: Portrait of a Killer: Who Was Orlando Nightclub Shooter Omar Mateen?

FBI Director James Comey said on Monday that while he stood behind his agency’s preliminary assessment into Mateen’s past, it’s exceedingly difficult to predict who among the many individuals on their radar would actually turn to violence. Mateen’s own motivations appear contradictory and not purely faith based — the gunman once claimed to be linked to two radical groups that violently oppose one another.

"We're looking for needles in a nationwide haystack. But we're also called upon to figure out which pieces of hay might someday become needles," FBI Director James Comey said during a press conference on Monday. "That is hard work."

The case exposes the pitfalls in combating “lone wolf” attacks on U.S. soil, tactics that, while encouraged by ISIS leaders, may or may not have direct ties to terrorism overseas. It becomes a slippery slope for policy makers when the potential perpetrators of attacks are American citizens.

Federal authorities have charged 88 people on terror-related offenses over the last two years, a significant rise in arrests unlike anything seen before. The vast majority of those charged were U.S. citizens or permanent residents.

In an exhaustive study of American recruits lured by terrorist groups, Seamus Hughes, an expert in homegrown extremism at George Washington University, found there was no clear profile to predict which individuals were likely to act on their extreme opinions and which were merely making a cry for help.

Related: Dealer Who Sold Orlando Massacre Guns: 'I Don't Make the Laws'

This creates a minefield of difficulties for law enforcement trying to walk a very fine line between taking an aggressive approach to counter terrorism and respecting the rights and civil liberties of American citizens.

"Our law enforcement are put into this untenable position of trying to prevent every single attack when you're never going to know what's in someone's mind," Hughes said. "How do you traverse those very difficult issues, especially in a country with a free society?"

Intertwined with the policy shortfalls is a contentious political debate over how to combat terrorism and gun violence. Suspected terror sympathizers can be placed under federal surveillance or on a no-fly list. Still, virtually nothing prevents them from legally obtaining a gun.

The Senate failed to pass an amendment in December that would have excluded suspected terrorists from buying guns and explosives. The stalemate mirrors other failed legislative efforts to strengthen background checks in the wake of equally devastating shooting tragedies in recent years.

President Obama has used the waning days of his second term to sharpen his criticism of policy inaction on gun violence, repeatedly raising the risk that existing gun laws did little to prevent suspected terrorists from loading up on legal firearms.

In fact, earlier this month, Obama came eerily close to predicting the exact circumstances that led up to Orlando's mass shooting.

Asked about gun control at a PBS town hall, Obama recounted a scene inside the Situation Room from just earlier that day. The FBI had identified a number of people, including U.S. citizens, who were active on websites associated with terror groups. Yet their hands were tied in ensuring those individuals could not become more dangerous.

"This is somebody who is a known ISIL (ISIS) sympathizer," Obama said. "And if he wants to walk into a gun store or a gun show right now and buy as much — as many weapons and ammo as he can, nothing's prohibiting him from doing that, even though the FBI knows who that person is."