'48 Hours' Reveals New Details in Deadly 1993 Waco Siege

New details will be revealed about the FBI's 1993 siege on the Waco, Texas cult of David Koresh in a 48 Hours special on CBS this Friday.

The event was the longest armed stand-off in U.S. history, lasting 51 days. In the first two-hour gun fight, 10 people were killed. In the end, Koresh and his followers burned the compound they lived on, claiming a total of 76 lives including that of Koresh himself.

Now on the 25th anniversary of the siege, 48 Hours has gathered new evidence and witnesses who weren't prepared to speak out before. Members of the Branch Davidian Church will appear on camera, explaining how Koresh indoctrinated them and why he had such power over so many people.

The main witness is Larry Gilbreath, who was a UPS driver in Waco when Koresh was in power. As the delivery driver, Gilbreath was one of the few outsiders to regularly set foot in the compound and see what the cult was up to firsthand. It turned out that many of the parcels he delivered were guns, ammunition, and even explosives.

"I've kept my story secret for 25 years," Gilbreath says in the preview of the new special. "I didn't want to take this to my grave."

The special also includes an interview with Grace Adams, a New Zealander who was recruited by Koresh and later escaped. She opens up about the abuse she suffered at his hands, including 4 months she spent imprisoned in a 10-foot by 8-foot room.

Adams details the way Koresh leveraged his position as a deity amongst his followers to get sex. She and other witnesses say Koresh slept with many girls as young as 12.

"As a woman, you needed to have sex with David in order to go to heaven," Adams says in the new special.

Investigators promise to explore the path that led Koresh to his extreme beliefs, and the charisma that allowed him to turn a religious community into a small army.

The special airs Friday, Dec. 29 at 8 p.m. ET.