Twenty years ago today, one of the best (and arguably last) films in the Die Hard franchise was released in theaters. Die Hard With a Vengeance featured the return of John McClane (Bruce Willis), again separated from his wife Holly and the kids after moving back to New York City. Throw in a random bystander-turned-partner in Zeus Carver (Samuel L. Jackson) and a faux-terrorist plot to rob the Federal Reserve Bank of all its gold bullion, and you’ve got yourself the franchise’s Lethal Weapon-inspired “buddy cop” installment.

I grew up watching the Die Hard trilogy with my brothers. (It became something of a Christmas tradition to marathon all three.) But it wasn’t until the 2007 release of the Die Hard Collection on DVD that I became fascinated with the movie’s major set piece — the robbery of the Federal Reserve Bank. That’s when I first listened to the commentary, which featured screenwriter Jonathan Hensleigh’s story about his being questioned by the FBI regarding his intimate knowledge of the Federal Reserve and the antagonist’s methods for robbing it.

Sure, whenever the film airs on AMC, its Story Notes program mentions it in the trivia blurb. The film’s IMDB page includes a brief mention in the “Trivia” section, too. But there’s nothing quite like the full story from Hensleigh himself.

Just read Hensleigh’s description of the “incursion into the basement” scene, after Simon and his goons take out the guards and the bank representative in the lobby:

This is now the incursion into the basement of the Federal Reserve. These are Jack De Govia’s designs. All of this was built on a stage — these cages here, with the gold behind it. This is very, very much the way the basement vault of the Federal Reserve in New York actually looks. This actually looks a little sexier, a little more interesting, but it’s kind of like that. It’s kind of low-tech hallways. It’s not all chrome or stainless steel. It just looks like regular hallways and corridors. The vault itself has those cages. It really does look like that.

His knowledge of what the Federal Reserve Bank’s basement vaults look like, or at least his confidence in the matter, seems circumspect. Sure, Hensleigh is a professional writer and filmmaker, and the more research he and his ilk do, the better. But don’t you think something like a government bank would have better control over its layouts?

That’s what the New York Police Department and the Federal Bureau of Investigation thought, too — which is why the latter pulled Hensleigh aside for questioning during the film’s pre-production:

When the script was being vetted by all the authorities in New York, obviously the New York Police Department had to read the script for a number of reasons. One day I got a call from the FBI. They were extremely concerned about how I knew so much about the Federal Reserve, and how the Federal Reserve’s vaults were really close to a subway spur, and logistically about the aqueduct tunnel, etc.

So, not only were the authorities worried about how and why Hensleigh had such intimate knowledge of the Federal Reserve Bank’s schematics, but they were also interested in his antagonist’s plan of escape. Aqueducts being used by massive dump trucks in and out of Manhattan? Really? How would he even know that was feasible?

I said, “Well guys, the reason why I know what the vault looks like in the Federal Reserve is because they let us down there. They showed it to us. The reason why I know that a subway spur is very close to the vault and that you could actually tunnel through it is because they showed us the plans and the layout. And the reason why I know there is an aqueduct tunnel coming down through Manhattan that you can drives these trucks through is because I read about it in the New York Times Sunday Magazine. So I’m really not employed by Afghani terrorists. I really don’t have any kind of secret proprietary knowledge that I shouldn’t have.”

What it comes down to is, Hensleigh was just being a good researcher. Sure, the bank robber wearing a terrorist attacker’s mask was copied from the plot of Die Hard, but the screenwriter had done enough of his homework to create a workable plot that audiences would believe throughout the film’s 131-minute running time.

That being said, Hensleigh didn’t take the episode lightly. At one point in the commentary, he admits the interrogation “kind of scared the sh*t out of me for about 10 minutes” because he “thought they were going to arrest me.” But at the same time he was frightened by it all, the FBI’s response to the script gave him confidence in the film’s success. It even made him a little proud: