An unidentified “senior law enforcement official” tells the New York Times that, while the FBI had been aware of Garland, Texas jihadist attacker Elton Simpson for nearly a decade, they did not follow his violent, pro-jihad tweets as closely as they could have because “there are so many like him” that the agency is overwhelmed.

In a report highlighting the long paper trail Simpson left behind of supporting and engaging with jihadists online, particualrly on Twitter, the Times notes that the sheer barrage of information can make it difficult for law enforcement to identify legitimate and imminent threats out of a sea of wishful jihadist thinkers.

Simpson and his roommate, Nadir Soofi, attacked a “Draw Muhammad” art contest in Garland, Texas on Sunday armed with assault rifles. They were almost immediately neutralized by a traffic officer working at the Culwell Center in Garland, and managed only to shoot one officer in the leg before their demise.

The New York Times notes that, while the center was heavily monitored due to a barrage of terrorist threats online, Simpson himself had only been cursorily monitored. He nonetheless was extremely active on Twitter: “Mr. Simpson, a convert to Islam with a long history of extremism, regularly traded calls for violence on Twitter with Islamic State fighters and supporters, as well as avowed enemies of Pamela Geller, the organizer of the cartoon contest.”

Simpson appeared to be communicating extensively in particular with Mohamed Abduhallahi Hassan, an American who is currently waging jihad with the terrorist group Al-Shabaab in Somalia. Hassan is believed to have been the first jihadist online to highlight the Draw Muhammad contest and call for an attack on the event.

Despite Simpson’s public calls for jihad on Twitter, one law enforcement official told the New York Times that this did not make him unique or demanding of special monitoring. “The ISIS guys are talking to these wannabes on Twitter all day long,” the official told the New York Times. “It’s like the devil is sitting on their shoulder saying, ‘Come on, they’re insulting the prophet, what are you going to do about it?’”

The official added that “There are so many like him that you have to prioritize your investigations.”

The statement is particularly concerning following a press release by the Islamic State claiming that there are at least 71 active Islamic State members in the United States, trained to kill. CNN’s Peter Bergen claims law enforcement is aware of 62 recruits to ISIS, the al-Nusra front, or similar groups, with ethnic and socioeconomic backgrounds so varied that it is extremely difficult to predict where new recruits will come from. The most predictable behavior they share, he reports, is their love of publicly professing their commitment to jihad on social media:

These militants are also quite active on social media. This is something of a boon for law enforcement, as many of these militants are prolific posters on publicly available social media, which it is perfectly legal for the FBI and police departments to monitor. […] The only profile that ties together American militants drawn to the Syrian conflict is that they are active in online jihadist circles.

In none of the known cases was there a direct physical meeting or phone conversation with a member of a terrorist group; the ties had all been forged online.

United States attempts to counter ISIS recruiting online previously have greatly failed. “Think Again, Turn Away,” a program by the Center for Strategic Counterterrorism Communications consisting mostly of a government Twitter account scolding jihadists in public tweets, has largely been considered a failure, with the head of SITE Intelligence Group calling it a “gaffe machine,” “distressing,” and “embarrassing.” In February, the New York Times reported that President Obama had ordered a major overhaul of both the center and the program, focusing on not just dissuasion on social media, but “coordinat[ing] and amplify[ing] similar messaging by foreign allies and nongovernment agencies, as well as by prominent Muslim academics, community leaders and religious scholars who oppose the Islamic State… and who may have more credibility with ISIS’ target audience of young men and women than the American government.”