It’s been nearly 25 years since a fire engulfed the Mount Carmel Center of the Branch Davidians in Waco, TX, killing 76 people, including cult leader David Koresh. Now, in an upcoming 48 Hours special called Secrets of Waco, a retired Texas United Parcel Service driver is breaking his silence about how he “unwittingly delivered large boxes of military grade guns and ammunition” to David’s controversial congregation prior to the 51-day standoff between the church and FBI officials in 1993.

"I thought it was a little strange that religious people would be ordering guns,” former delivery driver Larry Gilbreath says in a preview, adding that he noticed the packages got bigger and bigger over time. "And I'd say probably 75 percent of the time, when I would get there, David always came out. He signed for a lot of ‘em."

larry gillbreath - cbs
CBS

Larry Gillbreath.

According to Gillbreath, he delivered various types of weapons, including 223s, AK-47s, ART-15s, “and even a grenade launcher.” However, in February 1992, a package of grenades opened before Gillbreath could deliver them. It was then that he decided to alert law enforcement — and started cooperating with the FBI in an effort to save those who were subject to Koresh’s emotional, physical, and sexual abuse.

"And outta nowhere, David just looks at me, and says, 'Larry, I know they're watching us,'" Gilbreath says in the sneak peek, recalling the chilling moment he knew Koresh was intent on starting a war with the government. "I went numb.”

To this day, Gillbreath — who says he “didn’t wanna take this to [his] grave” — can’t help but feel somewhat responsible for the deaths that occurred because of the armed fight between Koresh, his followers, and the FBI. "Yes, of course [I still feel haunted]. How could you not, how could we not feel that maybe, like I say, we're not the ones that called in the ATF. The sheriff's department did," Gilbreath says. "We paid a pretty good price. I have been blamed for the — what happened out there.”

In Secrets of Waco, 48 Hours also interviews law enforcement agents, Koresh disciples, and survivors of the standoff. Grace Adams, who escaped Koresh’s compound after being trapped in a 10-foot by eight-foot room for four months, says that the self-proclaimed prophet sexually abused girls as young as 12 years old.

“As a woman, you needed to have sex with David in order to go to heaven,” says Adams, who admits that her time spent in confinement was mentally taxing. “I was treated like a prisoner. My mind did get messed up.”

Though there has been much dispute over the fire that concluded the FBI’s siege on the Branch Davidians’ compound, an internal Justice Department investigation concluded in 2000 that sect members themselves had set flames to the building after dismissing the FBI’s negations for a peaceful surrender.

Secrets of Waco airs on CBS Friday, Dec. 29, at 8 p.m. EST.