On Sunday’s broadcast of CBS’s “60 Minutes,” Anderson Cooper moderated a segment about the difficulties of monitoring potential domestic ISIS sympathizers by law enforcement.

At the end of the segment, Dan Maynard, an attorney for Abdul Malik Abdul Kareem, an Arizona man convicted of helping the two men that carried out an attack on a 2015 “Draw Muhammed” art contest in Garland, TX, Elton Simpson and Nadir Soofi, revealed an undercover FBI agent had been tracking Simpson and Soofi right up to moments before they carried out the attack.

According to Cooper’s report, the undercover agent fled the scene and was even stopped and handcuffed by Garland, TX police.

Partial transcript as follows:

ANDERSON COOPER: [H]is attorney Dan Maynard continued to investigate, and uncovered new evidence the FBI was much closer to the Garland attack than anyone realized. After the trial, you discovered that the government knew a lot more about the Garland attack than they had let on?

DAN MAYNARD: That’s right. Yeah. After the trial we found out that they had had an undercover agent who had been texting with Simpson, less than three weeks before the attack, to him “Tear up Texas,” which to me was an encouragement to Simpson.

COOPER: The man he’s talking about was a special agent of the FBI, working undercover posing as an Islamic radical. The government sent attorney Dan Maynard 60 pages of declassified encrypted messages between the agent and Elton Simpson – and argued “Tear up Texas” was not an incitement. But Simpson’s response was incriminating, referring to the attack against cartoonists at the French magazine Charlie Hebdo: “bro, you don’t have to say that…” He wrote “you know what happened in Paris… so that goes without saying. No need to be direct.”

But it turns out the undercover agent did more than just communicate online with Elton Simpson. In an affidavit filed in another case the government disclosed that the FBI undercover agent had actually “traveled to Garland, Texas, and was present… at the event.”

MAYNARD: I was shocked. I mean I was shocked that the government hadn’t turned this over. I wanted to know when did he get there, why was he there?

COOPER: And this past November, Maynard was given another batch of documents by the government, revealing the biggest surprise of all. The undercover FBI agent was in a car directly behind Elton Simpson and Nadir Soofi when they started shooting. This cell-phone photo of school security guard Bruce Joiner and police officer Greg Stevens was taken by the undercover agent seconds before the attack.

The idea that he’s taking photographs of the two people who happen to be attacked moments before they’re attacked.

MAYNARD: It’s stunning.

COOPER: I mean, talk about being in the right or the wrong place at the right or the wrong time.

MAYNARD: The idea that he’s right there 30 seconds before the attack happens is just incredible to me.

COOPER: What would you want to ask the undercover agent?

MAYNARD: I would love to ask the undercover agent– Are these the only communications that you had with Simpson? Did you have more communications with Simpson? How is it that you ended up coming to Garland, Texas? Why are you even there?

COOPER: We wanted to ask the FBI those same questions. But the bureau would not agree to an interview. All the FBI would give us was this email statement. It reads: “There was no advance knowledge of a plot to attack the cartoon drawing contest in Garland, Texas.”

If you’re wondering what happened to the FBI’s undercover agent, he fled the scene but was stopped at gunpoint by Garland police. This is video of him in handcuffs, recorded by a local news crew. We’ve blurred his face to protect his identity.

MAYNARD: I can’t tell you whether the FBI knew the attack was gonna occur. I don’t like to think that they let it occur. But it is shocking to me that an undercover agent sees fellas jumping out of a car and he drives on. I find that shocking.

COOPER: That he didn’t try to stop–

MAYNARD: He didn’t try to stop ‘em. Or he didn’t do something. I mean, he’s an agent, for gosh sakes.

COOPER: If this attack had gone a different way, and lots of people had been killed, would the fact that an undercover FBI agent was on the scene have become essentially a scandal?

SEAMUS HUGHES: It woulda been a bigger story. I think you would have seen congressional investigations and things like that. Lucky for the FBI and for the participants in the event you know, here in Texas, you know, everyone’s a good shot there.

The FBI’s actions around this foiled attack offer a rare glimpse into the complexities faced by those fighting homegrown extremism. Today, the battle often begins online where identifying terrorists can be the difference between a massacre, and the one that never occurred in Garland, Texas.

Follow Jeff Poor on Twitter @jeff_poor